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<div class="app">
<h1 style="text-align: center;">Hacker's Guide to Subversion</h1>
<p>If you are contributing code to the Subversion project, please read
this first.</p>
<pre>
$LastChangedDate$
</pre>
<!-- Other pages seem to use "h2" for ToC, but I think "h1" works
better, because the ToC is fundamentally different from other
sections and therefore it's confusing when it looks the same as
the others. -->
<div class="h1"><!-- no 'id' or 'title' attribute for ToC -->
<h1>Table of Contents</h1>
<ul>
<li><a href="#participating"
>Participating in the community</a></li>
<li><a href="#docs"
>Theory and documentation</a></li>
<li><a href="#code-to-read"
>Code to read</a></li>
<li><a href="#directory-layout"
>Directory layout</a></li>
<li><a href="#coding-style"
>Coding style</a></li>
<li><a href="#secure-coding"
>Secure coding guidelines</a></li>
<li><a href="#destruction-of-stacked-resources"
>Destruction of stacked resources</a></li>
<li><a href="#documenting"
>Document everything</a></li>
<li><a href="#use-page-breaks"
>Using page breaks</a></li>
<li><a href="#error-messages"
>Error message conventions</a></li>
<li><a href="#other-conventions"
>Other conventions</a></li>
<li><a href="#apr-pools"
>APR pool usage conventions</a></li>
<li><a href="#apr-status-codes"
>APR status codes</a></li>
<li><a href="#exception-handling"
>Exception handling</a></li>
<li><a href="#automated-tests"
>Automated tests</a></li>
<li><a href="#write-test-cases-first"
>Writing test cases before code</a></li>
<li><a href="#server-debugging"
>Debugging the server</a></li>
<li><a href="#tracing-memory-leaks"
>Tracking down memory leaks</a></li>
<li><a href="#log-messages"
>Writing log messages</a></li>
<li><a href="#crediting"
>Crediting</a></li>
<li><a href="#patches"
>Patch submission guidelines</a></li>
<li><a href="#filing-issues"
>Filing bugs / issues</a></li>
<li><a href="#commit-access"
>Commit access</a></li>
<li><a href="#configury"
>The configuration/build system under unix</a></li>
<li><a href="#releasing"
>How to release a distribution tarball</a></li>
<li><a href="#release-numbering"
>Release numbering, compatibility, and deprecation</a></li>
<li><a href="#release-stabilization"
>Stabilizing and maintaining releases</a></li>
<li><a href="#tarball-signing"
>Signing source distribution packages</a></li>
<li><a href="#l10n"
>Localization (l10n)</a></li>
</ul>
</div>
<div class="h2" id="participating" title="participating">
<h2>Participating in the community</h2>
<p>Although Subversion is originally sponsored and hosted by CollabNet
(<a href="http://www.collab.net">http://www.collab.net</a>), it's a
true open-source project under a BSD-style license. A number of
developers work for CollabNet, some work for other large companies
(such as RedHat), and many others are simply excellent volunteers who
are interested in building a better version control system.</p>
<p>The community exists mainly through mailing lists and a Subversion
repository. To participate:</p>
<p>Go to <a href="http://subversion.tigris.org/"
>http://subversion.tigris.org/</a> and</p>
<ul>
<li><p>Join the "dev", "svn", and "announce" mailing lists.
The dev list, dev@subversion.tigris.org, is where almost all
discussion takes place. All development questions should go
there, though you might want to check the list archives first.
The "svn" list receives automated commit emails.</p></li>
<li><p>Get a copy of the latest development sources from
<a href="http://svn.collab.net/repos/svn/trunk/"
>http://svn.collab.net/repos/svn/trunk/</a>.
<br />
New development always takes place on trunk. Bugfixes,
enhancements, and new features are backported from there to the
various release branches.</p></li>
</ul>
<p>There are many ways to join the project, either by writing code, or
by testing and/or helping to manage the bug database. If you'd like
to contribute, then look at:</p>
<ul>
<li><p>The bugs/issues database
<a href="http://subversion.tigris.org/project_issues.html"
>http://subversion.tigris.org/project_issues.html</a></p></li>
<li><p>The bite-sized tasks page
<a href="http://subversion.tigris.org/project_tasks.html"
>http://subversion.tigris.org/project_tasks.html</a></p></li>
</ul>
<p>To submit code, simply send your patches to
dev@subversion.tigris.org. No, wait, first read the rest of this
file, <i>then</i> start sending patches to
dev@subversion.tigris.org. :-)</p>
<p>To help manage the issues database, read over the issue summaries,
looking and testing for issues that are either invalid, or are
duplicates of other issues. Both kinds are very common, the first
because bugs often get unknowingly fixed as side effects of other
changes in the code, and the second because people sometimes file an
issue without noticing that it has already been reported. If you are
not sure about an issue, post a question to dev@subversion.tigris.org.
("Subversion: We're here to help you help us!")</p>
<p>Another way to help is to set up automated builds and test suite
runs of Subversion on some platform, and have the output sent to the
svn-breakage@subversion.tigris.org mailing list. See more details at
<a href="http://subversion.tigris.org/servlets/ProjectMailingListList"
>http://subversion.tigris.org/servlets/ProjectMailingListList</a>
in the description for the svn-breakage list.</p>
</div>
<div class="h2" id="docs" title="docs">
<h2>Theory and documentation</h2>
<ol>
<li><p>Design</p>
<p>A <a href="design.html">design spec</a> was written in June 2000,
and is a bit out of date. But it still gives a good theoretical
introduction to the inner workings of the repository, and to
Subversion's various layers.</p>
</li>
<li><p>API documentation</p>
<p>The <a href="http://svn.collab.net/svn-doxygen/">API documentation</a>
is generated by Doxygen from the C header files and gives detailed
information about all functions, types and so on available in the
Subversion API. </p>
</li>
<li> <p>Network Protocols</p>
<p>The <a href="webdav-usage.html">WebDAV Usage</a> document is
an introduction to Subversion's ra_dav network protocol, which is
an extended dialect of HTTP and uses URLs beginning with
"http://" or "https://".</p>
<p>The <a
href="http://svn.collab.net/repos/svn/trunk/subversion/libsvn_ra_svn/protocol"
>SVN Protocol</a> document contains a formal description of
Subversion ra_svn network protocol, which is a custom protocol
on port 3690 (by default), whose URLs begin with "svn://" or
"svn+ssh://".</p>
</li>
<li><p>User Manual</p>
<p>Version Control with Subversion is a book published by
O'Reilly that shows in detail how to effectively use Subversion.
The text of the book is free, and is actively being revised.
On-line versions are available
at <a href="http://svnbook.red-bean.com"
>http://svnbook.red-bean.com</a>. The XML source and
translations to other languages are maintained in their own
repository at <a href="http://svn.red-bean.com/svnbook"
>http://svn.red-bean.com/svnbook</a>.</p>
</li>
<li><p>System notes</p>
<p>A lot of the design ideas for particular aspects of the system
have been documented in individual files in the
<a href="http://svn.collab.net/repos/svn/trunk/notes/">notes/</a>
directory.</p>
</li>
</ol>
</div>
<div class="h2" id="code-to-read" title="code-to-read">
<h2>Code to read</h2>
<p>Before you can contribute code, you'll need to familiarize yourself
with the existing code base and interfaces.</p>
<p>Check out a copy of Subversion (anonymously, if you don't yet have
an account with commit access)&nbsp;&mdash;&nbsp;so you can look at
the code.</p>
<p>Within 'subversion/include/' are a bunch of header files with huge
doc comments. If you read through these, you'll have a pretty good
understanding of the implementation details. Here's a suggested
perusal order:</p>
<ol>
<li><p>the basic building blocks: svn_string.h, svn_error.h, svn_types.h</p>
</li>
<li><p>useful utilities: svn_io.h, svn_path.h, svn_hash.h, svn_xml.h</p>
</li>
<li><p>the critical interface: svn_delta.h</p>
</li>
<li><p>client-side interfaces: svn_ra.h, svn_wc.h, svn_client.h</p>
</li>
<li><p>the repository and versioned filesystem: svn_repos.h, svn_fs.h</p>
</li>
</ol>
<p>Subversion tries to stay portable by using only ANSI/ISO C and by
using the Apache Portable Runtime (APR) library. APR is the
portability layer used by the Apache httpd server, and more
information can be found at <a href="http://apr.apache.org/"
>http://apr.apache.org/</a>.</p>
<p>Because Subversion depends so heavily on APR, it may be hard to
understand Subversion without first glancing over certain header files
in APR (look in 'apr/include/'):</p>
<ul>
<li><p>memory pools: apr_pools.h</p></li>
<li><p>filesystem access: apr_file_io.h</p></li>
<li><p>hashes and arrays: apr_hash.h, apr_tables.h</p></li>
</ul>
<p>Subversion also tries to deliver reliable and secure software. This
can only be achieved by developers who understand secure programming
in the C programming language. Please see 'notes/assurance.txt' for
the full rationale behind this. Specifically, you should make it a
point to carefully read David Wheeler's Secure Programming (as
mentioned in 'notes/assurance.txt'). If at any point you have
questions about the security implications of a change, you are urged
to ask for review on the developer mailing list.</p>
</div>
<div class="h2" id="directory-layout" title="directory-layout">
<h2>Directory layout</h2>
<p>A rough guide to the source tree:</p>
<ul>
<li><p><tt>doc/</tt><br />
User and Developer documentation.</p>
</li>
<li><p><tt>www/</tt><br />
Subversion web pages (live content at
<a href="http://subversion.tigris.org/"
>http://subversion.tigris.org/</a>).</p>
</li>
<li><p><tt>tools/</tt><br />
Stuff that works with Subversion, but that Subversion doesn't
depend on. Code in tools/ is maintained collectively by the
Subversion project, and is under the same open source copyright as
Subversion itself.</p>
</li>
<li><p><tt>contrib/</tt><br />
Stuff that works with Subversion, but that Subversion doesn't
depend on, and that is maintained by individuals who may or may
not participate in Subversion development. Code in contrib/ is
open source, but may have a different license or copyright holder
than Subversion itself.</p>
</li>
<li><p><tt>packages/</tt><br />
Stuff to help packaging systems, like rpm and dpkg.</p>
</li>
<li><p><tt>subversion/</tt><br />
Source code to Subversion itself (as opposed to external
libraries).</p>
</li>
<li><p><tt>subversion/include/</tt><br />
Public header files for users of Subversion libraries.</p>
</li>
<li><p><tt>subversion/libsvn_fs/</tt><br />
The versioning "filesystem" API.</p>
</li>
<li><p><tt>subversion/libsvn_repos/</tt><br />
Repository functionality built around the `libsvn_fs' core.</p>
</li>
<li><p><tt>subversion/libsvn_delta/</tt><br />
Common code for tree deltas, text deltas, and property deltas.</p>
</li>
<li><p><tt>subversion/libsvn_wc/</tt><br />
Common code for working copies.</p>
</li>
<li><p><tt>subversion/libsvn_ra/</tt><br />
Common code for repository access.</p>
</li>
<li><p><tt>subversion/libsvn_client/</tt><br />
Common code for client operations.</p>
</li>
<li><p><tt>subversion/svn/</tt><br />
The command line client.</p>
</li>
<li><p><tt>subversion/tests/</tt><br />
Automated test suite.</p>
</li>
<li><p><tt>apr/</tt><br />
Apache Portable Runtime library. (Note: This is not in the same
repository as Subversion. Read INSTALL for instructions on how to
get it if you don't already have it.)</p>
</li>
<li><p><tt>neon/</tt><br />
Neon library from Joe Orton. (Note: This is not in the same
repository as Subversion. Read INSTALL for instructions on how to
get it if you don't already have it.)</p>
</li>
</ul>
</div>
<div class="h2" id="coding-style" title="coding-style">
<h2>Coding style</h2>
<p>Subversion uses ANSI C, and follows the GNU coding standards,
except that we do not put a space between the name of a function and
the opening parenthesis of its parameter list. Emacs users can just
load svn-dev.el to get the right indentation behavior (most source
files here will load it automatically, if `enable-local-eval' is set
appropriately).</p>
<p>Read <a href="http://www.gnu.org/prep/standards.html"
>http://www.gnu.org/prep/standards.html</a> for a full description of
the GNU coding standards. Below is a short example demonstrating the
most important formatting guidelines, including our
no-space-before-param-list-paren exception:</p>
<pre>
char * /* func type on own line */
argblarg(char *arg1, int arg2) /* func name on own line */
{ /* first brace on own line */
if ((some_very_long_condition &amp;&amp; arg2) /* indent 2 cols */
|| remaining_condition) /* new line before operator */
{ /* brace on own line, indent 2 */
arg1 = some_func(arg1, arg2); /* NO SPACE BEFORE PAREN */
} /* close brace on own line */
else
{
do /* format do-while like this */
{
arg1 = another_func(arg1);
}
while (*arg1);
}
}
</pre>
<p>In general, be generous with parentheses even when you're sure
about the operator precedence, and be willing to add spaces and
newlines to avoid "code crunch". Don't worry too much about vertical
density; it's more important to make code readable than to fit that
extra line on the screen.</p>
</div>
<div class="h2" id="secure-coding" title="secure-coding">
<h2>Secure coding guidelines</h2>
<p>Just like almost any other programming language, C has undesirable
features which enables an attacker to make your program fail in
predictable ways, often to the attacker's benefit. The goal of these
guidelines is to make you aware of the pitfalls of C as they apply to
the Subversion project. You are encouraged to keep these pitfalls in
mind when reviewing code of your peers, as even the most skilled and
paranoid programmers make occasional mistakes.</p>
<p>Input validation is the act of defining legal input and rejecting
everything else. The code must perform input validation on all
untrusted input. </p>
<p>Security boundaries:</p>
<p>A security boundary in the Subversion server code must be
identified as such as this enables auditors to quickly determine the
quality of the boundary. Security boundaries exist where the running
code has access to information the user does not or where the code
runs with privileges above those of the user making the
request. Typical examples of such is code that does access control or
an application with the SUID bit set.</p>
<p>Functions which make calls to a security boundary must include
validation checks of the arguments passed. Functions which themselves
are security boundaries should audit the input received and alarm when
invoked with improper values. </p>
<p>[### todo: need some examples from Subversion here...]</p>
<p>String operations:</p>
<p>Use the string functions provided in apr_strings.h instead of
standard C library functions that write to strings. The APR functions
are safer because they do bounds-checking and dest allocation
automatically. Although there may be circumstances where it's
theoretically safe to use plain C string functions (such as when you
already know the lengths of the source and dest), please use the APR
functions anyway, so the code is less brittle and more reviewable.</p>
<p>Password storage:</p>
<p>Help users keep their passwords secret: When the client reads or
writes password locally, it should ensure that the file is mode
0600. If the file is readable by other users, the client should exit
with a message that tells the user to change the filemode due to the
risk of exposure.</p>
</div>
<div class="h2" id="destruction-of-stacked-resources"
title="destruction-of-stacked-resources">
<h2>Destruction of stacked resources</h2>
<p>Some resources need destruction to ensure correct functioning of the
application. Such resources include files, especially since open
files cannot be deleted on Windows.</p>
<p>When writing an API which creates and returns a stream, in the
background this stream may be stacked on a file or other stream. To
ensure correct destruction of the resources the stream is built upon,
it must correctly call the destructors of the stream(s) it is built
upon (owns).</p>
<p>At first in <a href="http://svn.haxx.se/dev/archive-2005-12/0487.shtml">
http://svn.haxx.se/dev/archive-2005-12/0487.shtml</a>
and later in <a href="http://svn.haxx.se/dev/archive-2005-12/0633.shtml">
http://svn.haxx.se/dev/archive-2005-12/0633.shtml</a> this
was discussed in more general terms for files, streams, editors and
window handlers.</p>
<p>As Greg Hudson put it:</p>
<blockquote>
<p>On consideration, here is where I would like us to be:</p>
<ul><li>Streams which read from or write to an underlying object own that
object, i.e. closing the stream closes the underlying object, if
applicable.</li>
<li>The layer (function or data type) which created a stream is
responsible for closing it, except when the above rule applies.</li>
<li>Window handlers are thought of as an odd kind of stream, and passing
the final NULL window is considered closing the stream.</li>
</ul>
<p>If you think of apply_textdelta as creating a window handler, then I
don't think we're too far off. svn_stream_from_aprfile isn't owning its
subsidiary file, svn_txdelta_apply is erroneously taking responsibility
for closing the window stream it is passed, and there may be some other
deviations.</p>
</blockquote>
<p>There is one exception to the rules above though. When a stream is passed
to a function as an argument (for example: the 'out' parameter of
svn_client_cat2()), that routine can't call the streams destructor, since
it did not create that resource.</p>
<p>If svn_client_cat2() creates a stream, it must also call the destructor
for that stream. By the above model, that stream will call the destructor
for the 'out' parameter. This is however wrong, because the responsibility
to destruct the 'out' parameter lies elsewhere.</p>
<p>To solve this problem, at least in the stream case, svn_stream_disown()
has been introduced. This function wraps a stream, making sure it's
<em>not</em> destroyed, even though any streams stacked upon it may try
to do so.</p>
</div>
<div class="h2" id="documenting" title="documenting">
<h2>Document everything</h2>
<p>Every function, whether public or internal, must start out with a
documentation comment that describes what the function does. The
documentation should mention every parameter received by the function,
every possible return value, and (if not obvious) the conditions under
which the function could return an error.</p>
<p>For internal documentation put the parameter names in upper case
in the doc string, even when they are not upper case in the actual
declaration, so that they stand out to human readers.</p>
<p>Use the <a href="http://www.doxygen.org/">Doxygen</a> format for
public interface documentation. This means anything that goes in a
public header file.</p>
<p>For public or semi-public API functions, the doc string should go
above the function in the .h file where it is declared; otherwise, it
goes above the function definition in the .c file.</p>
<p>For structure types, document each individual member of the
structure as well as the structure itself.</p>
<p>Read over the Subversion code to get an overview of how
documentation looks in practice; in particular, see
subversion/include/*.h for doxygen examples.</p>
</div>
<div class="h2" id="use-page-breaks" title="use-page-breaks">
<h2>Using page breaks</h2>
<p>We're using page breaks (the Ctrl-L character, ASCII 12) for
section boundaries in both code and plaintext prose files. Each
section starts with a page break, and immediately after the page break
comes the title of the section.</p>
<p>This helps out people who use the Emacs page commands, such as
`pages-directory' and `narrow-to-page'. Such people are not as scarce
as you might think, and if you'd like to become one of them, then add
(require 'page-ext) to your .emacs and type C-x C-p C-h sometime.</p>
</div>
<div class="h2" id="error-messages" title="error-messages">
<h2>Error message conventions</h2>
<p>For error messages the following conventions apply:</p>
<ul>
<li><p>Provide specific error messages only when there is information
to add to the general error message found in
subversion/include/svn_error_codes.h.</p></li>
<li><p>Messages start with a capital letter.</p></li>
<li><p>Try keeping messages below 70 characters.</p></li>
<li><p>Don't end the error message with a period (".").</p></li>
<li><p>Don't include newline characters in error messages.</p></li>
<li><p>Quoting information is done using single quotes (e.g. "'some info'").</p></li>
<li><p>Don't include the name of the function where the error occurs
in the error message. If Subversion is compiled using the
'--enable-maintainer-mode' configure-flag, it will provide this
information by itself.</p></li>
<li><p>When including path or filenames in the error string, be sure
to quote them (e.g. "Can't find '/path/to/repos/userfile'").</p></li>
<li><p>When including path or filenames in the error string, be sure
to convert them using 'svn_path_local_style()' before inclusion.</p></li>
<li><p>Don't use Subversion-specific abbreviations (e.g. use "repository"
instead of "repo", "working copy" instead of "wc").</p></li>
<li><p>If you want to add an explanation to the error, report it
followed by a colon and the explanation like this:</p>
<pre>
"Invalid " SVN_PROP_EXTERNALS " property on '%s': "
"target involves '.' or '..'".
</pre></li>
<li><p>Suggestions or other additions can be added after a semi-colon,
like this:</p>
<pre>
"Can't write to '%s': object of same name already exists; remove "
"before retrying".
</pre></li>
<li><p>Try to stay within the boundaries of these conventions, so please avoid
separating different parts of error messages by other separators such
as '--' and others.</p></li>
</ul>
<p>Also read about <a href="#l10n">Localization</a>.</p>
</div>
<div class="h2" id="other-conventions" title="other-conventions">
<h2>Other conventions</h2>
<p>In addition to the GNU standards, Subversion uses these
conventions:</p>
<ul>
<li><p>Use only spaces for indenting code, never tabs. Tab display
width is not standardized enough, and anyway it's easier to
manually adjust indentation that uses spaces.</p>
</li>
<li><p>Restrict lines to 79 columns, so that code will display well in a
minimal standard display window. (There can be exceptions, such
as when declaring a block of 80-column text with a few extra
columns taken up by indentation, quotes, etc., if splitting each
line in two would be unreasonably messy.)</p>
</li>
<li><p>All published functions, variables, and structures must be signified
with the corresponding library name - such as libsvn_wc's
svn_wc_adm_open. All library-internal declarations made in a
library-private header file (such as libsvn_wc/wc.h) must be signified
by two underscores after the library prefix (such as
svn_wc__ensure_directory). All declarations private to a single file
(such as the static function get_entry_url inside
libsvn_wc/update_editor.c) do not require any additional namespace
decorations. Symbols that need to be used outside a library, but
still are not public are put in a public header, but use the
double underscore notation. Such symbols may be used by
Subversion core code only, and we try to be restrictive
regarding the introduction of such entities.</p>
<p>To recap:</p>
<pre>
/* Part of published API: subversion/include/svn_wc.h */
svn_wc_adm_open()
#define SVN_WC_ADM_DIR_NAME ...
typedef enum svn_wc_schedule_t ...
/* For use within one library only: subversion/libsvn_wc/wc.h */
svn_wc__ensure_directory()
#define SVN_WC__BASE_EXT ...
typedef struct svn_wc__compat_notify_baton_t ...
/* For use within one file: subversion/libsvn_wc/update_editor.c */
get_entry_url()
struct handler_baton {
/* For internal use in svn core code only:
subversion/include/svn_types.h */
#define SVN__STREAM_CHUNK_SIZE
/* subversion/include/svn_error.h */
void svn_error__locate(const char *file, long line);
</pre>
</li>
<li><p>In text strings that might be printed out (or otherwise made
available) to users, use only forward quotes around paths and
other quotable things. For example:</p>
<pre>
$ svn revert foo
svn: warning: svn_wc_is_wc_root: 'foo' is not a versioned resource
$
</pre>
<p>There used to be a lot of strings that used a backtick for
the first quote (`foo' instead of 'foo'), but that looked bad in
some fonts, and also messed up some people's auto-highlighting,
so we settled on the convention of always using forward
quotes.</p>
</li>
<li><p>If you use Emacs, put something like this in your .emacs file,
so you get svn-dev.el and svnbook.el when needed:</p>
<pre>
;;; Begin Subversion development section
(defun my-find-file-hook ()
(let ((svn-tree-path (expand-file-name "~/projects/subversion"))
(book-tree-path (expand-file-name "~/projects/svnbook")))
(cond
((string-match svn-tree-path buffer-file-name)
(load (concat svn-tree-path "/tools/dev/svn-dev")))
((string-match book-tree-path buffer-file-name)
;; Handle load exception for svnbook.el, because it tries to
;; load psgml, and not everyone has that available.
(condition-case nil
(load (concat book-tree-path "/src/tools/svnbook"))
(error
(message "(Ignored problem loading svnbook.el.)")))))))
(add-hook 'find-file-hooks 'my-find-file-hook)
;;; End Subversion development section
</pre>
<p>You'll need to customize the path for your setup, of course.
You can also make the regexp to string-match more selective; for
example, one developer says:</p>
<pre>
&gt; Here's the regexp I'm using:
&gt;
&gt; "src/svn/[^/]*/\\(subversion\\|tools\\|build\\)/"
&gt;
&gt; Two things to notice there: (1) I sometimes have several
&gt; working copies checked out under ...src/svn, and I want the
&gt; regexp to match all of them; (2) I want the hook to catch only
&gt; in "our" directories within the working copy, so I match
&gt; "subversion", "tools" and "build" explicitly; I don't want to
&gt; use GNU style in the APR that's checked out into my repo. :-)
</pre>
</li>
<li><p>We have a tradition of not marking files with the names of
individual authors (i.e., we don't put lines like
"Author:&nbsp;foo" or "@author&nbsp;foo" in a special position
at the top of a source file). This is to discourage
territoriality&nbsp;&mdash;&nbsp;even when a file has only one
author, we want to make sure others feel free to make changes.
People might be unnecessarily hesitant if someone appears to
have staked a personal claim to the file.</p>
</li>
<li><p>Put two spaces between the end of one sentence and the start of
the next. This helps readability, and allows people to use
their editors' sentence-motion and -manipulation commands.</p>
</li>
<li><p>There are many other unspoken conventions maintained throughout
the code, that are only noticed when someone unintentionally
fails to follow them. Just try to have a sensitive eye for the
way things are done, and when in doubt, ask.</p>
</li>
</ul>
</div>
<div class="h2" id="apr-pools" title="apr-pools">
<h2>APR pool usage conventions</h2>
<p>(This assumes you already basically understand how APR pools work;
see apr_pools.h for details.)</p>
<p>Applications using the Subversion libraries must call
apr_initialize() before calling any Subversion functions.</p>
<p>Subversion's general pool usage strategy can be summed up in two
principles:</p>
<ol>
<li><p>The call level that created a pool is the only place to clear or
destroy that pool.</p>
</li>
<li><p>When iterating an unbounded number of times, create a subpool
before entering the iteration, use it inside the loop and clear
it at the start of each iteration, then destroy it after the loop
is done, like so:</p>
<pre>
apr_pool_t *subpool = svn_pool_create(pool);
for (i = 0; i &lt; n; ++i)
{
svn_pool_clear(subpool);
do_operation(..., subpool);
}
svn_pool_destroy(subpool);
</pre>
</li>
</ol>
<p>By using a loop subpool for loop-bounded data, you ensure O(1) instead
of O(N) memory leakage should the function return abruptly from
within the loop (say, due to error). That's why you shouldn't make a
subpool for data which persists throughout a function, but instead
should use the pool passed in by the caller. That memory will be
reclaimed when the caller's pool is cleared or destroyed. If the
caller is invoking the callee in a loop, then trust the caller to take
care of clearing the pool on each iteration. The same logic
propagates all the way up the call stack.</p>
<p>The pool you use also helps readers of the code understand object
lifetimes. Is a given object used only during one iteration of the
loop, or will it need to last beyond the end of the loop? For
example, pool choices indicate a lot about what's going on in this
code:</p>
<pre>
apr_hash_t *persistent_objects = apr_hash_make(pool);
apr_pool_t *subpool = svn_pool_create(pool);
for (i = 0; i &lt; n; ++i)
{
const char *intermediate_result;
const char *key, *val;
svn_pool_clear(subpool);
SVN_ERR(do_something(&amp;intermediate_result, ..., subpool));
SVN_ERR(get_result(intermediate_result, &amp;key, &amp;val, ..., pool));
apr_hash_set(persistent_objects, key, APR_HASH_KEY_STRING, val);
}
svn_pool_destroy(subpool);
return persistent_objects;
</pre>
<p>Except for some legacy code, which was written before these
principles were fully understood, virtually all pool usage in
Subversion follows the above guidelines.</p>
<p>One such legacy pattern is a tendency to allocate an object inside
a pool, store the pool in the object, and then free that pool (either
directly or through a close_foo() function) to destroy the object.</p>
<p>For example:</p>
<pre>
<span style="color: red;">/*** Example of how NOT to use pools. Don't be like this. ***/</span>
static foo_t *
make_foo_object(arg1, arg2, apr_pool_t *pool)
{
apr_pool_t *subpool = svn_pool_create(pool);
foo_t *foo = apr_palloc(subpool, sizeof(*foo));
foo-&gt;field1 = arg1;
foo-&gt;field2 = arg2;
foo-&gt;pool = subpool;
}
[...]
[Now some function calls make_foo_object() and returns, passing
back a new foo object.]
[...]
[Now someone, at some random call level, decides that the foo's
lifetime is over, and calls svn_pool_destroy(foo-&gt;pool).]
</pre>
<p>This is tempting, but it defeats the point of using pools, which is
to not worry so much about individual allocations, but rather about
overall performance and lifetime groups. Instead, foo_t generally
should not have a `pool' field. Just allocate as many foo objects as
you need in the current pool&nbsp;&mdash;&nbsp;when that pool gets
cleared or destroyed, they will all go away simultaneously.</p>
<p>See also the <a href="#exception-handling">Exception handling</a>
section, for details of how resources associated with a pool are
cleaned up when that pool is destroyed.</p>
<p>In summary:</p>
<ul>
<li><p>Objects should not have their own pools. An object is
allocated into a pool defined by the constructor's caller. The
caller knows the lifetime of the object and will manage it via
the pool.</p>
</li>
<li><p>Functions should not create/destroy pools for their operation;
they should use a pool provided by the caller. Again, the
caller knows more about how the function will be used, how
often, how many times, etc. thus, it should be in charge of the
function's memory usage.</p>
<p>For example, the caller might know that the app will exit upon
the function's return. Thus, the function would create extra
work if it built/destroyed a pool. Instead, it should use the
passed-in pool, which the caller is going to be tossing as part
of app-exit anyway.</p>
</li>
<li><p>Whenever an unbounded iteration occurs, an iteration subpool
should be used.</p>
</li>
<li><p>Given all of the above, it is pretty well mandatory to pass a
pool to every function. Since objects are not recording pools
for themselves, and the caller is always supposed to be
managing memory, then each function needs a pool, rather than
relying on some hidden magic pool. In limited cases, objects
may record the pool used for their construction so that they
can construct sub-parts, but these cases should be examined
carefully.</p>
</li>
</ul>
<p>See also <a href="#tracing-memory-leaks">Tracking down memory
leaks</a> for tips on diagnosing pool usage problems.</p>
</div>
<div class="h2" id="apr-status-codes" title="apr-status-codes">
<h2>APR status codes</h2>
<p>Always check for APR status codes (except APR_SUCCESS) with the
APR_STATUS_IS_...() macros, not by direct comparison. This is required
for portability to non-Unix platforms.</p>
</div>
<div class="h2" id="exception-handling" title="exception-handling">
<h2>Exception handling</h2>
<p>OK, here's how to use exceptions in Subversion.</p>
<ol>
<li><p>Exceptions are stored in svn_error_t structures:</p>
<pre>
typedef struct svn_error
{
apr_status_t apr_err; /* APR error value, possibly SVN_ custom err */
const char *message; /* details from producer of error */
struct svn_error *child; /* ptr to the error we "wrap" */
ap_pool_t *pool; /* place to generate message strings from */
const char *file; /* Only used iff SVN_DEBUG */
long line; /* Only used iff SVN_DEBUG */
} svn_error_t;
</pre>
</li>
<li><p>If you are the *original* creator of an error, you would do
something like this:</p>
<pre>
return svn_error_create(SVN_ERR_FOO, NULL,
"User not permitted to write file");
</pre>
<p>NOTICE the NULL field... indicating that this error has no
child, i.e. it is the bottom-most error.</p>
<p>See also the <a href="#error-messages"> section on writing
error messages</a>.</p>
<p>Subversion internally uses UTF-8 to store its data. This also
applies to the 'message' string. APR is assumed to return its data
in the current locale, so any text returned by APR needs
conversion to UTF-8 before inclusion in the message string.</p>
</li>
<li><p>If you *receive* an error, you have three choices:</p>
<ol>
<li><p>Handle the error yourself. Use either your own code, or
just call the primitive svn_handle_error(err). (This
routine unwinds the error stack and prints out messages
converting them from UTF-8 to the current locale.)</p>
<p>When your routine receives an error which it intends to
ignore or handle itself, be sure to clean it up using
svn_error_clear(). Any time such an error is not cleared
constitutes a *memory leak*.</p>
</li>
<li><p>Throw the error upwards, unmodified:</p>
<pre>
error = some_routine(foo);
if (error)
return (error);
</pre>
<p>Actually, a better way to do this would be with the
SVN_ERR() macro, which does the same thing:</p>
<pre>
SVN_ERR(some_routine(foo));
</pre>
</li>
<li><p>Throw the error upwards, wrapping it in a new error
structure by including it as the "child" argument:</p>
<pre>
error = some_routine(foo);
if (error)
{
svn_error_t *wrapper = svn_error_create(SVN_ERR_FOO, error,
"Authorization failed");
return wrapper;
}
</pre>
<p>Of course, there's a convenience routine which creates a
wrapper error with the same fields as the child, except for
your custom message:</p>
<pre>
error = some_routine(foo);
if (error)
{
return svn_error_quick_wrap(error,
"Authorization failed");
}
</pre>
<p>The same can (and should) be done by using the SVN_ERR_W()
macro:</p>
<pre>
SVN_ERR_W(some_routine(foo), "Authorization failed");
</pre>
</li>
</ol>
<p>In cases (b) and (c) it is important to know that resources
allocated by your routine which are associated with a pool, are
automatically cleaned up when the pool is destroyed. This means
that there is no need to cleanup these resources before passing
the error. There is therefore no reason not to use the SVN_ERR()
and SVN_ERR_W() macros. Resources associated with pools are:</p>
<ul>
<li><p>Memory</p></li>
<li><p>Files</p>
<p>All files opened with apr_file_open are closed at pool
cleanup. Subversion uses this function in its svn_io_file_*
api, which means that files opened with svn_io_file_* or
apr_file_open will be closed at pool cleanup.</p>
<p>Some files (lock files for example) need to be removed when
an operation is finished. APR has the APR_DELONCLOSE flag for
this purpose. The following functions create files which are
removed on pool cleanup:</p>
<ul>
<li><p>apr_file_open and svn_io_file_open (when passed the
APR_DELONCLOSE flag)</p></li>
<li><p>svn_io_open_unique_file (when passed TRUE in its
delete_on_close)</p></li>
</ul>
<p>Locked files are unlocked if they were locked using
svn_io_file_lock.</p>
</li>
</ul>
</li>
</ol>
</div>
<div class="h2" id="automated-tests" title="automated-tests">
<h2>Automated tests</h2>
<p>For a description of how to use and add tests to Subversion's
automated test framework, please read <a
href="http://svn.collab.net/repos/svn/trunk/subversion/tests/README"
>subversion/tests/README</a> and <a
href="http://svn.collab.net/repos/svn/trunk/subversion/tests/cmdline/README"
>subversion/tests/cmdline/README</a>.</p>
<p>Various people have arranged for the automated test framework to
run at regular intervals on their own machines, sending the results to
the svn-breakage@subversion.tigris.org mailing list. The more
different platforms the tests run on, the more quickly we can detect
portability bugs in Subversion. If you'd like to send svn-breakage
messages too, use the <a
href="http://svn.collab.net/repos/svn/trunk/tools/test-scripts/svntest/"
>svntest</a> framework (start at the <a
href="http://svn.collab.net/repos/svn/trunk/tools/test-scripts/svntest/README"
>README</a>).</p>
<p>Lieven Govaerts has set up a
<a href="http://buildbot.sourceforge.net/" >BuildBot</a> build/test
farm at <a href="http://www.mobsol.be/buildbot/"
>http://www.mobsol.be/buildbot/</a>, see his message</p>
<pre>
<a href="http://subversion.tigris.org/servlets/ReadMsg?list=dev&amp;msgNo=114212">http://subversion.tigris.org/servlets/ReadMsg?list=dev&amp;msgNo=114212</a>
(Thread URL: <a href="http://subversion.tigris.org/servlets/BrowseList?list=dev&amp;by=thread&amp;from=450110">http://subversion.tigris.org/servlets/BrowseList?list=dev&amp;by=thread&amp;from=450110</a>)
Message-ID: 20060326205918.F3C50708B0@adicia.telenet-ops.be
From: "Lieven Govaerts" &lt;lgo@mobsol.be&gt;
To: &lt;dev@subversion.tigris.org&gt;
Subject: Update: Subversion build and test farm with Buildbot.
Date: Sun, 26 Mar 2006 22:56:11 +0200
</pre>
<p>for more details. (<a href="http://buildbot.sourceforge.net/"
>BuildBot</a> is a system for centrally managing multiple automated
testing environments; it's especially useful for portability testing,
including of uncommitted changes.)</p>
</div>
<div class="h2" id="write-test-cases-first" title="write-test-cases-first">
<h2>Writing test cases before code</h2>
<pre>
From: Karl Fogel &lt;kfogel@collab.net&gt;
Subject: writing test cases
To: dev@subversion.tigris.org
Date: Mon, 5 Mar 2001 15:58:46 -0600
Many of us implementing the filesystem interface have now gotten into
the habit of writing the test cases (see fs-test.c) *before* writing
the actual code. It's really helping us out a lot -- for one thing,
it forces one to define the task precisely in advance, and also it
speedily reveals the bugs in one's first try (and second, and
third...).
I'd like to recommend this practice to everyone. If you're
implementing an interface, or adding an entirely new feature, or even
just fixing a bug, a test for it is a good idea. And if you're going
to write the test anyway, you might as well write it first. :-)
Yoshiki Hayashi's been sending test cases with all his patches lately,
which is what inspired me to write this mail to encourage everyone to
do the same. Having those test cases makes patches easier to examine,
because they show the patch's purpose very clearly. It's like having
a second log message, one whose accuracy is verified at run-time.
That said, I don't think we want a rigid policy about this, at least
not yet. If you encounter a bug somewhere in the code, but you only
have time to write a patch with no test case, that's okay -- having
the patch is still useful; someone else can write the test case.
As Subversion gets more complex, though, the automated test suite gets
more crucial, so let's all get in the habit of using it early.
-K
</pre>
</div>
<div class="h2" id="server-debugging" title="server-debugging">
<h2>Debugging the server</h2>
<div class="h3" id="debugging-ra-dav" title="debugging-ra-dav">
<h3>Debugging the ra_dav server</h3>
<p>'mod_dav_svn.so' contains the main Subversion server logic; it runs
as a module within mod_dav, which runs as a module within httpd.
Since httpd is probably using dynamic shared modules, you normally
won't be able to set breakpoints in advance when you start Apache in a
debugger such as GDB. Instead, you'll need to start up, then
interrupt httpd, set your breakpoint, and continue:</p>
<pre>
% gdb httpd
(gdb) run -X
^C
(gdb) break some_func_in_mod_dav_svn
(gdb) continue
</pre>
<p>The -X switch is equivalent to -DONE_PROCESS and -DNO_DETACH, which
ensure that httpd runs as a single thread and remains attached to the
tty, respectively. As soon as it starts, it sits and waits for
requests; that's when you hit control-C and set your breakpoint.</p>
<p>You'll probably want to watch Apache's run-time logs</p>
<pre>
/usr/local/apache2/logs/error_log
/usr/local/apache2/logs/access_log
</pre>
<p>to help determine what might be going wrong and where to set
breakpoints.</p>
</div>
<div class="h3" id="debugging-ra-svn" title="debugging-ra-svn">
<h3>Debugging the ra_svn client and server, on Unix</h3>
<p>Bugs in ra_svn usually manifest themselves with one of the
following cryptic error messages:</p>
<pre>
svn: Malformed network data
svn: Connection closed unexpectedly
</pre>
<p>(The first message can also mean the data stream was corrupted in
tunnel mode by user dotfiles or hook scripts; see
<a href="http://subversion.tigris.org/issues/show_bug.cgi?id=1145"
>issue&nbsp;#1145</a>.) The first message generally means you to have
to debug the client; the second message generally means you have to
debug the server.</p>
<p>It is easiest to debug ra_svn using a build with --disable-shared
--enable-maintainer-mode. With the latter option, the error message
will tell you exactly what line to set a breakpoint at; otherwise,
look up the line number at the end of marshal.c:vparse_tuple() where
it returns the "Malformed network data" error.</p>
<p>To debug the client, simply pull it up in gdb, set a breakpoint,
and run the offending command:</p>
<pre>
% gdb svn
(gdb) break marshal.c:NNN
(gdb) run ARGS
Breakpoint 1, vparse_tuple (list=___, pool=___, fmt=___,
ap=___) at subversion/libsvn_ra_svn/marshal.c:NNN
NNN "Malformed network data");
</pre>
<p>There are several bits of useful information:</p>
<ul>
<li><p>A backtrace will tell you exactly what protocol exchange is
failing.</p>
</li>
<li><p>"print *conn" will show you the connection buffer. read_buf,
read_ptr, and read_end represent the read buffer, which can
show
you the data the marshaller is looking at. (Since read_buf isn't
generally 0-terminated at read_end, be careful of falsely assuming
that there's garbage data in the buffer.)</p>
</li>
<li><p>The format string determines what the marshaller was expecting to
see.</p>
</li>
</ul>
<p>To debug the server in daemon mode, pull it up in gdb, set a
breakpoint (usually a "Connection closed unexpectedly" error on the
client indicates a "Malformed network data" error on the server,
although it can also indicate a core dump), and run it with the "-X"
option to serve a single connection:</p>
<pre>
% gdb svnserve
(gdb) break marshal.c:NNN
(gdb) run -X
</pre>
<p>Then run the offending client command. From there, it's just like
debugging the client.</p>
<p>Debugging the server in tunnel mode is more of a pain. You'll need
to stick something like "{ int x = 1; while (x); }" near the top of
svnserve's main() and put the resulting svnserve in the user path on
the server. Then start an operation, gdb attach the process on the
server, "set x = 0", and step through the code as desired.</p>
</div>
</div>
<div class="h2" id="tracing-memory-leaks" title="tracing-memory-leaks">
<h2>Tracking down memory leaks</h2>
<p>Our use of APR pools makes it unusual for us to have memory leaks
in the strictest sense; all the memory we allocate will be cleaned up
eventually. But sometimes an operation takes more memory than it
should; for instance, a checkout of a large source tree should not use
much more memory than a checkout of a small source tree. When that
happens, it generally means we're allocating memory from a pool whose
lifetime is too long.</p>
<p>If you have a favorite memory leak tracking tool, you can configure
with --enable-pool-debug (which will make every pool allocation use
its own malloc()), arrange to exit in the middle of the operation, and
go to it. If not, here's another way:</p>
<ul>
<li><p>Configure with --enable-pool-debug=verbose-alloc. Make sure to
rebuild all of APR and Subversion so that every allocation gets
file-and-line information.</p>
</li>
<li><p>Run the operation, piping stderr to a file. Hopefully you have
lots of disk space.</p>
</li>
<li><p>In the file, you'll see lots of lines which look like:</p>
<pre>
POOL DEBUG: [5383/1024] PCALLOC ( 2763/ 2763/ 5419) \
0x08102D48 "subversion/svn/main.c:612" \
&lt;subversion/libsvn_subr/auth.c:122&gt; (118/118/0)
</pre>
<p>What you care about most is the tenth field (the one in
quotes), which gives you the file and line number where the
pool for this allocation was created. Go to that file and line
and determine the lifetime of the pool. In the example above,
main.c:612 indicates that this allocation was made in the
top-level pool of the svn client. If this were an allocation
which was repeated many times during the course of an
operation, that would indicate a source of a memory leak. The
eleventh field (the one in brackets) gives the file and line
number of the allocation itself.</p>
</li>
</ul>
</div>
<div class="h2" id="log-messages" title="log-messages">
<h2>Writing log messages</h2>
<p>Every commit needs a log message. </p>
<p>The intended audience for a log message is a developer who is
already familiar with Subversion, but not necessarily familiar with
this particular commit. Usually when someone goes back and reads a
change, he no longer has in his head all the context around that
change. This is true even if he is the author of the change! All the
discussions and mailing list threads and everything else may be
forgotten; the only clue to what the change is about comes from the
log message and the diff itself. People revisit changes with
surprising frequency, too: for example, it might be months after the
original commit and now the change is being ported to a maintenance
branch.</p>
<p>The log message is the introduction to the change. Start it off
with one line indicating the general nature of the change, and follow
that with a descriptive paragraph if necessary. This not only helps
put developers in the right frame of mind for reading the rest of the
log message, but also plays well with the "CIA" bot that echoes the
first line of each commit to realtime forums like IRC. (For details,
see <a href="http://cia.navi.cx/">http://cia.navi.cx/</a>.) However,
if the commit is just one simple change to one file, then you can
dispense with the general description and simply go straight to the
detailed description, in the standard filename-then-symbol format
shown below.</p>
<p>Throughout the log message, use full sentences, not sentence
fragments. Fragments are more often ambiguous, and it takes only a
few more seconds to write out what you mean. Certain fragments like
"Doc fix", "New file", or "New function" are acceptable because they
are standard idioms, and all further details should appear in the
source code.</p>
<p>The log message should name every affected function, variable,
macro, makefile target, grammar rule, etc, including the names of
symbols that are being removed in this commit. This helps people
searching through the logs later. Don't hide names in wildcards,
because the globbed portion may be what someone searches for later.
For example, this is bad:</p>
<pre>
* subversion/libsvn_ra_pigeons/twirl.c
(twirling_baton_*): Removed these obsolete structures.
(handle_parser_warning): Pass data directly to callees, instead
of storing in twirling_baton_*.
* subversion/libsvn_ra_pigeons/twirl.h: Fix indentation.
</pre>
<p>Later on, when someone is trying to figure out what happened to
`twirling_baton_fast', they may not find it if they just search for
"_fast". A better entry would be:</p>
<pre>
* subversion/libsvn_ra_pigeons/twirl.c
(twirling_baton_fast, twirling_baton_slow): Removed these
obsolete structures.
(handle_parser_warning): Pass data directly to callees, instead
of storing in twirling_baton_*.
* subversion/libsvn_ra_pigeons/twirl.h: Fix indentation.
</pre>
<p>The wildcard is okay in the description for
`handle_parser_warning', but only because the two structures were
mentioned by full name elsewhere in the log entry.</p>
<p>Note how each file gets its own entry prefixed with an "*", and the
changes within a file are grouped by symbol, with the symbols listed
in parentheses followed by a colon, followed by text describing the
change. Please adhere to this format, even when only one file is
changed&nbsp;&mdash;&nbsp;not only does consistency aid readability,
it also allows software to colorize log entries automatically.</p>
<p>As an exception to the above, if you make exactly the same change
in several files, list all the changed files in one entry. For
example:</p>
<pre>
* subversion/libsvn_ra_pigeons/twirl.c,
subversion/libsvn_ra_pigeons/roost.c:
Include svn_private_config.h.
</pre>
<p>If all the changed files are deep inside the source tree, you can
shorten the file name entries by noting the common prefix before the
change entries:</p>
<pre>
[in subversion/bindings/swig/birdsong]
* dialects/nightingale.c (get_base_pitch): Allow 3/4-tone
pitch variation to account for trait variability amongst
isolated populations Erithacus megarhynchos.
* dialects/gallus_domesticus.c: Remove. Unreliable due to
extremely low brain-to-body mass ratio.
</pre>
<p>If your change is related to a specific issue in the issue tracker,
then include a string like "issue #N" in the log message, but make
sure you still summarize what the change is about. For example, if a
patch resolves issue #1729, then the log message might be:</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
</pre>
<p>Try to put related changes together. For example, if you create
svn_ra_get_ansible2(), deprecating svn_ra_get_ansible(), then those
two things should be near each other in the log message:</p>
<pre>
* subversion/include/svn_ra.h
(svn_ra_get_ansible2): New prototype, obsoletes svn_ra_get_ansible.
(svn_ra_get_ansible): Deprecate.
</pre>
<p>For large changes or change groups, group the log entry into
paragraphs separated by blank lines. Each paragraph should be a set
of changes that accomplishes a single goal, and each group should
start with a sentence or two summarizing the change. Truly
independent changes should be made in separate commits, of course.</p>
<p>See <a href="#crediting">Crediting</a> for how to give credit to
someone else if you are committing their patch, or committing a change
they suggested.</p>
<p>One should never need the log entries to understand the current
code. If you find yourself writing a significant explanation in the
log, you should consider carefully whether your text doesn't actually
belong in a comment, alongside the code it explains. Here's an
example of doing it right:</p>
<pre>
(consume_count): If `count' is unreasonable, return 0 and don't
advance input pointer.
</pre>
<p>And then, in `consume_count' in `cplus-dem.c':</p>
<pre>
while (isdigit((unsigned char)**type))
{
count *= 10;
count += **type - '0';
/* A sanity check. Otherwise a symbol like
`_Utf390_1__1_9223372036854775807__9223372036854775'
can cause this function to return a negative value.
In this case we just consume until the end of the string. */
if (count &gt; strlen(*type))
{
*type = save;
return 0;
}
</pre>
<p>This is why a new function, for example, needs only a log entry
saying "New Function" --- all the details should be in the source.</p>
<p>You can make common-sense exceptions to the need to name everything
that was changed. For example, if you have made a change which
requires trivial changes throughout the rest of the program (e.g.,
renaming a variable), you needn't name all the functions affected, you
can just say "All callers changed". However, if you rename symbols
(e.g., to add or remove a library prefix), please mention every
affected symbol, both old and new&nbsp;&mdash;&nbsp;this is the only
way the rename of a particular symbol would be traceable later. See
r20946 for an example of this.</p>
<p>In general, there is a tension between making entries easy to find
by searching for identifiers, and wasting time or producing unreadable
entries by being exhaustive. Use the above guidelines and your best
judgment, and be considerate of your fellow developers. (Also, run
"svn log" to see how others have been writing their log entries.)</p>
<p>Log messages for documentation or translation have somewhat looser
guidelines. The requirement to name every symbol obviously does not
apply, and if the change is just one more increment in a continuous
process such as translation, it's not even necessary to name every
file. Just briefly summarize the change, for example: "More work on
Malagasy translation." Please write your log messages in English, so
everybody involved in the project can understand the changes you
made.</p>
</div>
<div class="h2" id="crediting" title="crediting">
<h2>Crediting</h2>
<p>It is very important to record code contributions in a consistent
and parseable way. This allows us to write scripts to figure out who
has been actively contributing&nbsp;&mdash;&nbsp;and what they have
contributed&nbsp;&mdash;&nbsp;so we can <a
href="http://www.red-bean.com/svnproject/contribulyzer/">spot
potential new committers quickly</a>. The Subversion project uses
human-readable but machine-parseable fields in log messages to
accomplish this.</p>
<p>When committing a patch written by someone else, use
"Patch&nbsp;by:&nbsp;" at the beginning of a line to indicate the
author:</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
Patch by: J. Random &lt;jrandom@example.com&gt;
</pre>
<p>If multiple individuals wrote the patch, list them each on a
separate line&nbsp;&mdash;&nbsp;making sure to start each continuation
line with whitespace. Non-committers should be listed by name, if
known, and e-mail. Committers may be listed similarly, or by their
canonical usernames from COMMITTERS (the leftmost column).
Additionally, "me" is an acceptable shorthand for the person actually
committing the change.</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
Patch by: J. Random &lt;jrandom@example.com&gt;
Enrico Caruso &lt;codingtenor@codingtenor.com&gt;
jcommitter
me
</pre>
<p>If someone found the bug or pointed out the problem, but didn't
write the patch, indicate their contribution with
"Found&nbsp;by:&nbsp;":</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
Found by: J. Random &lt;jrandom@example.com&gt;
</pre>
<p>If someone suggested something useful, but didn't write the patch,
indicate their contribution with "Suggested&nbsp;by:&nbsp;":</p>
<pre>
Extend the Contribulyzer syntax to distinguish finds from ideas.
* www/hacking.html (crediting): Adjust accordingly.
Suggested by: dlr
</pre>
<p>If someone reviewed the change, use "Review&nbsp;by:&nbsp;"
(or "Reviewed&nbsp;by:&nbsp;" if you prefer):</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
Review by: Eagle Eyes &lt;eeyes@example.com&gt;
</pre>
<p>A field may have multiple lines, and a log message may contain any
combination of fields:</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
Patch by: J. Random &lt;jrandom@example.com&gt;
Enrico Caruso &lt;codingtenor@codingtenor.com&gt;
me
Found by: J. Random &lt;jrandom@example.com&gt;
Review by: Eagle Eyes &lt;eeyes@example.com&gt;
jcommitter
</pre>
<p>Further details about a contribution should be listed in a
parenthetical aside immediately after the corresponding field. Such
an aside always applies to the field right above it; in the following
example, the fields have been spaced out for readability, but note
that the spacing is optional and not necessary for parseability:</p>
<pre>
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
Patch by: J. Random &lt;jrandom@example.com&gt;
(Tweaked by me.)
Review by: Eagle Eyes &lt;eeyes@example.com&gt;
jcommitter
(Eagle Eyes caught an off-by-one-error in the basename extraction.)
</pre>
<p>Currently, these fields</p>
<pre>
Patch by:
Suggested by:
Found by:
Review by:
</pre>
<p>are the only officially-supported crediting fields (where
"supported" means scripts know to look for them), and they are widely
used in Subversion log messages. Future fields will probably be of
the form "VERB&nbsp;by:&nbsp;", and from time to time someone may use
a field that sounds official but really is not&nbsp;&mdash;&nbsp;for
example, there are a few instances of "Reported&nbsp;by:&nbsp;".
These are okay, but try to use an official field, or a parenthetical
aside, in preference to creating your own. Also, don't use
"Reported&nbsp;by:&nbsp;" when the reporter is already recorded in an
issue; instead, simply refer to the issue.</p>
<p>Look over Subversion's existing log messages to see how to use
these fields in practice. This command from the top of your trunk
working copy will help:</p>
<pre>
svn log | contrib/client-side/search-svnlog.pl "(Patch|Review|Suggested) by: "
</pre>
<p><b>Note:</b> The "Approved&nbsp;by:&nbsp;" field seen in some
commit messages is totally unrelated to these crediting fields, and is
generally not parsed by scripts. It is simply the standard syntax for
indicating either who approved a partial committer's commit outside
their usual area, or (in the case of merges to release branches) who
voted for the change to be merged.</p>
</div>
<div class="h2" id="patches" title="patches">
<h2>Patch submission guidelines</h2>
<p>Mail patches to dev@subversion.tigris.org, with a subject line
that contains the word "PATCH" in all uppercase, for example</p>
<pre>
Subject: [PATCH] fix for rev printing bug in svn status
</pre>
<p>A patch submission should contain one logical change; please don't
mix N unrelated changes in one submission&nbsp;&mdash;&nbsp;send N
separate emails instead.</p>
<p>You can put the patch's log message in the body of the email, or at
the top of the patch attachment (see below). Either way, it should
follow the guidelines given in <a href="#log-messages">Writing
log messages</a>, and be enclosed in triple square brackets, like so:</p>
<pre>
[[[
Fix issue #1729: Don't crash because of a missing file.
* subversion/libsvn_ra_ansible/get_editor.c
(frobnicate_file): Check that file exists before frobnicating.
]]]
</pre>
<p>The brackets are not actually part of the log message, they are
just a way to clearly mark off the log message from its surrounding
context.</p>
<p>The patch itself should be in unified diff format (e.g., "svn diff"
or "diff -u"). Send the patch as an attachment, with a mime-type of
text/x-diff, text/x-patch, or text/plain. (Most people's mailreaders
can display those inline, and having the patch as an attachment allows
them to extract the patch from the message conveniently.)</p>
<p>If you can't attach the patch with one of these mime-types, or if
the patch is very short, then just include it directly in the body of
your message. But if your mailer forces wrapping of long lines, then
you must attach the patch, otherwise it is likely to get munged.
Never send patches in archived or compressed form (e.g., tar, gzip,
zip, bzip2), because that prevents people from reviewing the patch
directly in their mailreaders.</p>
<p>If the patch implements a new feature, make sure to describe the
feature completely in your mail; if the patch fixes a bug, describe
the bug in detail and give a reproduction recipe. An exception to
these guidelines is when the patch addresses a specific issue in the
issues database&nbsp;&mdash;&nbsp;in that case, just make sure to
refer to the issue number in your log message, as described
in <a href="#log-messages">Writing log messages</a>.</p>
<p>It is normal for patches to undergo several rounds of feedback and
change before being applied. Don't be discouraged if your patch is
not accepted immediately&nbsp;&mdash;&nbsp;it doesn't mean you goofed,
it just means that there are a *lot* of eyes looking at every code
submission, and it's a rare patch that doesn't have at least a little
room for improvement. After reading people's responses to your patch,
make the appropriate changes and resubmit, wait for the next round of
feedback, and lather, rinse, repeat, until some committer applies
it.</p>
<p>If you don't get a response for a while, and don't see the patch
applied, it may just mean that people are really busy. Go ahead and
repost, and don't hesitate to point out that you're still waiting for
a response. One way to think of it is that patch management is highly
parallizable, and we need you to shoulder your share of the management
as well as the coding. Every patch needs someone to shepherd it
through the process, and the person best qualified to do that is the
original submitter.</p>
<div class="h3" id="patch-manager" title="patch-manager">
<h3>The "Patch Manager" Role</h3>
<p>Subversion usually has a Patch Manager, whose job is to watch the
dev@ mailing list and make sure that no patches "slip through the
cracks".</p>
<p>This means watching every thread containing "[PATCH]" mails, and
taking appropriate action based on the progress of the thread. If the
thread resolves on its own (because the patch gets committed, or
because there is consensus that the patch doesn't need to be applied,
or whatever) then no further action need be taken. But if the thread
fades out without any clear decision, then the patch needs to be saved
in the issue tracker. This means that a summary of any discussion
threads around that patch, and links to relevant mailing list
archives, will be added to some issue in the tracker. For a patch
which addresses an existing issue tracker item, the patch is saved to
that item. Otherwise, a new issue of type 'PATCH' is filed, and the
patch is saved to that new issue.</p>
<p>The Patch Manager needs a basic technical understanding of
Subversion, and the ability to skim a thread and get a rough
understanding of whether consensus has been reached, and if so, of
what kind. It does *not* require actual Subversion development
experience or commit access. Expertise in using one's mail reading
software is optional, but recommended :-).</p>
<p>The current patch manager is Hyrum Wright
&lt;hyrum_wright@mail.utexas.edu&gt;.</p>
</div>
</div>
<div class="h2" id="filing-issues" title="filing-issues">
<h2>Filing bugs / issues</h2>
<p>This pretty much says it all:</p>
<pre>
From: Karl Fogel &lt;kfogel@collab.net&gt;
Subject: Please ask on the list before filing a new issue.
To: dev@subversion.tigris.org
Date: Tue, 30 Jul 2002 10:51:24 (CDT)
Folks, we're getting tons of new issues, which is a Good Thing in
general, but some of them don't really belong in the issue tracker.
They're things that would be better solved by a quick conversation
here on the dev list. Compilation problems, behavior questions,
feature ideas that have been discussed before, that sort of thing.
*Please* be more conservative about filing issues. The issues
database is physically much more cumbersome than email. It wastes
people's time to have conversations in the issues database that should
be had in email. (This is not a libel against the issue tracker, it's
just a result of the fact that the issues database is for permanent
storage and flow annotation, not for real-time conversation.)
If you encounter a situation where Subversion is clearly behaving
wrongly, or behaving opposite to what the documentation says, then
it's okay to file the issue right away (after searching to make sure
it isn't already filed, of course!). But if you're
a) Requesting a new feature, or
b) Having build problems, or
c) Not sure what the behavior should be, or
d) Disagreeing with current intended behavior, or
e) Not TOTALLY sure that others would agree this is a bug, or
f) For any reason at all not sure this should be filed,
...then please post to the dev list first. You'll get a faster
response, and others won't be forced to use the issues database to
have the initial real-time conversations.
Nothing is lost this way. If we eventually conclude that it should be
in the issue tracker, then we can still file it later, after the
description and reproduction recipe have been honed on the dev list.
Thank you,
-Karl
</pre>
</div>
<div class="h2" id="commit-access" title="commit-access">
<h2>Commit access</h2>
<p>There are two types of commit access: full and partial. Full means
anywhere in the tree, partial means only in that committer's specific
area(s) of expertise. The COMMITTERS file lists all committers, both
full and partial, and says the domains for each partial committer.</p>
<div class="h3" id="full-commit-access" title="full-commit-access">
<h3>How full commit access is granted</h3>
<p>After someone has successfully contributed a few non-trivial
patches, some full committer, usually whoever has reviewed and applied
the most patches from that contributor, proposes them for commit
access. This proposal is sent only to the other full committers --
the ensuing discussion is private, so that everyone can feel
comfortable speaking their minds. Assuming there are no objections,
the contributor is granted commit access. The decision is made by
consensus; there are no formal rules governing the procedure, though
generally if someone strongly objects the access is not offered, or is
offered on a provisional basis.</p>
<p><i>The primary criterion for full commit access is good
judgment.</i></p>
<p>You do not have to be a technical wizard, or demonstrate deep
knowledge of the entire codebase, to become a full committer. You
just need to know what you don't know. If your patches adhere to the
guidelines in this file, adhere to all the usual unquantifiable rules
of coding (code should be readable, robust, maintainable, etc.), and
respect the Hippocratic Principle of "first, do no harm", then you
will probably get commit access pretty quickly. The size, complexity,
and quantity of your patches do not matter as much as the degree of
care you show in avoiding bugs and minimizing unnecessary impact on
the rest of the code. Many full committers are people who have not
made major code contributions, but rather lots of small, clean fixes,
each of which was an unambiguous improvement to the code. (Of course,
this does not mean the project needs a bunch of very trivial patches
whose only purpose is to gain commit access; knowing what's worth a
patch post and what's not is part of showing good judgement :-) .)</p>
<p>To assist developers in discovering new committers, we record
patches and other contributions in a <a href="#crediting">special
crediting format</a>, which is then parsed to produce a
browser-friendly <a
href="http://www.red-bean.com/svnproject/contribulyzer/">contribution
list</a>, updated nightly. If you're thinking of proposing someone
for commit access and want to look over all their changes, that <a
href="http://www.red-bean.com/svnproject/contribulyzer/">contribution
list</a> might be the most convenient place to do it.</p>
</div>
<div class="h3" id="partial-commit-access" title="partial-commit-access">
<h3>How partial commit access is granted</h3>
<p>A full committer sponsors the partial committer. Usually this
means the full committer has applied several patches to the same area
from the proposed partial committer, and realizes things would be
easier if the person were just committing directly. Approval is not
required from the full committers; it is assumed that sponsors know
what they're doing and will watch the partial committer's first few
commits to make sure everything's going smoothly.</p>
<p>Patches submitted by a partial committer may be committed by that
committer even if they are outside that person's domain. This
requires approval (often expressed as a +1 vote) from at least one
full committer. In such a case, the approval should be noted in the
log message, like so:</p>
<pre>
Approved by: lundblad
</pre>
</div>
<div class="h3" id="contrib-area" title="contrib-area">
<h3>The contrib/ area</h3>
<p>When a tool is accepted into the <i>contrib/</i> area, we
automatically offer its author partial commit access to maintain the
tool there. Any full committer can sponsor this. Usually no
discussion or vote is necessary, though if there are objections then
the usual decision-making procedures apply (attempt to reach consensus
first, then vote among the full committers if consensus cannot be
reached).</p>
<p>Code under contrib/ must be open source, but need not have the same
license or copyright holder as Subversion itself.</p>
</div>
<div class="h3" id="obvious-fix" title="obvious-fix">
<h3>The "obvious fix" rule</h3>
<p>Any committer, whether full or partial, may commit fixes for
obvious typos, grammar mistakes, and formatting problems wherever they
may be&nbsp;&mdash;&nbsp;in the web pages, API documentation, code
comments, commit messages, etc. We rely on the committer's judgement
to determine what is "obvious"; if you're not sure, just ask.</p>
</div>
</div>
<div class="h2" id="configury" title="configury">
<h2>The configuration/build system under unix</h2>
<p>Greg Stein wrote a custom build system for Subversion, which had
been using `automake' and recursive Makefiles. Now it uses a single,
top-level Makefile, generated from Makefile.in (which is kept under
revision control). `Makefile.in' in turn includes `build-outputs.mk',
which is automatically generated from `build.conf' by the
`gen-make.py' script. Thus, the latter two are under revision
control, but `build-outputs.mk' is not.</p>
<p>Here is Greg's original mail describing the system, followed by
some advice about hacking it:</p>
<pre>
From: Greg Stein &lt;gstein@lyra.org&gt;
Subject: new build system (was: Re: CVS update: MODIFIED: ac-helpers ...)
To: dev@subversion.tigris.org
Date: Thu, 24 May 2001 07:20:55 -0700
Message-ID: &lt;20010524072055.F5402@lyra.org&gt;
On Thu, May 24, 2001 at 01:40:17PM -0000, gstein@tigris.org wrote:
&gt; User: gstein
&gt; Date: 01/05/24 06:40:17
&gt;
&gt; Modified: ac-helpers .cvsignore svn-apache.m4
&gt; Added: . Makefile.in
&gt; Log:
&gt; Switch over to the new non-recursive build system.
&gt;...
Okay... this is it. We're now on the build system.
"It works on my machine."
I suspect there may be some tweaks to make on different OSs. I'd be
interested to hear if Ben can really build with normal BSD make. It
should be possible.
The code supports building, installation, checking, and
dependencies. It does *NOT* yet deal with the doc/ subdirectory. That
is next; I figured this could be rolled out and get the kinks worked
out while I do the doc/ stuff. Oh, it doesn't build Neon or APR yet
either. I also saw a problem where libsvn_fs wasn't getting built
before linking one of the test proggies (see below).
Basic operation: same as before.
$ ./autogen.sh
$ ./configure OPTIONS
$ make
$ make check
$ make install
There are some "make check" scripts that need to be fixed up. That'll
happen RSN. Some of them create their own log, rather than spewing to
stdout (where the top-level make will place the output into
[TOP]/tests.log).
The old Makefile.am files are still around, but I'll be tossing those
along with a bunch of tweaks to all the .cvsignore files. There are a
few other cleanups, too. But that can happen as a step two.
[ $ cvs rm -f `find . -name Makefile.rm`
See the mistake in that line? I didn't when I typed it. The find
returned nothing, so cvs rm -f proceeded to delete my entire
tree. And the -f made sure to delete all my source files, too. Good
fugging thing that I had my mods in some Emacs buffers, or I'd be
bitching.
I am *so* glad that Ben coded SVN to *not* delete locally modified
files *and* that we have an "undel" command. I had to go and tweak a
bazillion Entries files to undo the delete...
]
The top-level make has a number of shortcuts in it (well, actually in
build-outputs.mk):
$ make subversion/libsvn_fs/libsvn_fs.la
or
$ make libsvn_fs
The two are the same. So... when your test proggie fails to link
because libsvn_fs isn't around, just run "make libsvn_fs" to build it
immediately, then go back to the regular "make".
Note that the system still conditionally builds the FS stuff based
on whether DB (See 'Building on Unix' below) is available, and
mod_dav_svn if Apache is available.
Handy hint: if you don't like dependencies, then you can do:
$ ./autogen.sh -s
That will skip the dependency generation that goes into
build-outputs.mk. It makes the script run quite a bit faster (48 secs
vs 2 secs on my poor little Pentium 120).
Note that if you change build.conf, you can simply run:
$ ./gen-make.py build.conf
to regen build-outputs.mk. You don't have to go back through the whole
autogen.sh / configure process.
You should also note that autogen.sh and configure run much faster now
that we don't have the automake crap. Oh, and our makefiles never
re-run configure on you out of the blue (gawd, I hated when automake
did that to me).
Obviously, there are going to be some tweaky things going on. I also
think that the "shadow" builds or whatever they're called (different
source and build dirs) are totally broken. Something tweaky will have
to happen there. But, thankfully, we only have one Makefile to deal
with.
Note that I arrange things so that we have one generated file
(build-outputs.mk), and one autoconf-generated file (Makefile from
.in). I also tried to shove as much logic/rules into
Makefile.in. Keeping build-outputs.mk devoid of rules (thus, implying
gen-make.py devoid of rules in its output generation) manes that
tweaking rules in Makefile.in is much more approachable to people.
I think that is about it. Send problems to the dev@ list and/or feel
free to dig in and fix them yourself. My next steps are mostly
cleanup. After that, I'm going to toss out our use of libtool and rely
on APR's libtool setup (no need for us to replicate what APR already
did).
Cheers,
-g
--
Greg Stein, http://www.lyra.org/
</pre>
<p>And here is some advice for those changing or testing the
configuration/build system:</p>
<pre>
From: Karl Fogel &lt;kfogel@collab.net&gt;
To: dev@subversion.tigris.org
Subject: when changing build/config stuff, always do this first
Date: Wed 28 Nov 2001
Yo everyone: if you change part of the configuration/build system,
please make sure to clean out any old installed Subversion libs
*before* you try building with your changes. If you don't do this,
your changes may appear to work fine, when in fact they would fail if
run on a truly pristine system.
This script demonstrates what I mean by "clean out". This is
`/usr/local/cleanup.sh' on my system. It cleans out the Subversion
libs (and the installed httpd-2.0 libs, since I'm often reinstalling
that too):
#!/bin/sh
# Take care of libs
cd /usr/local/lib
rm -f APRVARS
rm -f libapr*
rm -f libexpat*
rm -f libneon*
rm -f libsvn*
# Take care of headers
cd /usr/local/include
rm -f apr*
rm -f svn*
rm -f neon/*
# Take care of headers
cd /usr/local/apache2/lib
rm -f *
When someone reports a configuration bug and you're trying to
reproduce it, run this first. :-)
The voice of experience,
-Karl
</pre>
</div>
<div class="h2" id="releasing" title="releasing">
<h2>How to release a distribution tarball</h2>
<p>See <a href="release-process.html">The Subversion Release Procedure</a>.</p>
</div>
<div class="h2" id="release-numbering" title="release-numbering">
<h2>Release numbering, compatibility, and deprecation</h2>
<p>Subversion uses "MAJOR.MINOR.PATCH" release numbers, with the same
guidelines as APR (see <a href="http://apr.apache.org/versioning.html"
>http://apr.apache.org/versioning.html</a>), plus a few extensions,
described later. The general idea is:</p>
<ol>
<li><p>Upgrading/downgrading between different patch releases in the
same MAJOR.MINOR line never breaks code. It may cause bugfixes
to disappear/reappear, but API signatures and semantics remain
the same. (Of course, the semantics may change in the trivial
ways appropriate for bugfixes, just not in ways that would
force adjustments in calling code.)</p>
</li>
<li><p>Upgrading to a new minor release in the same major line may
cause new APIs to appear, but not remove any APIs. Any code
written to the old minor number will work with any later minor
number in that line. However, downgrading afterwards may not
work, if new code has been written that takes advantage of the
new APIs.</p>
</li>
<li><p>When the major number changes, all bets are off. This is the
only opportunity for a full reset of the APIs, and while we try
not to gratuitously remove interfaces, we will use it to clean
house a bit.</p>
</li>
</ol>
<p>Subversion extends the APR guidelines to cover client/server
compatibility questions:</p>
<ol>
<li><p>A patch or minor number release of a server (or client) never
breaks compatibility with a client (or server) in the same
major line. However, new features offered by the release might
be unsupported without a corresponding upgrade to the other
side of the connection. For updating ra_svn code specifically,
please observe these principles:</p>
<ol>
<li><p>Fields can be added to any tuple; old clients will simply
ignore them. (Right now, the marshalling implementation
does not let you put number or boolean values in the
optional part of a tuple, but changing that will not affect
the protocol.)</p>
<p>We can use this mechanism when information is added to an
API call.</p>
</li>
<li><p>At connection establishment time, clients and servers exchange
a list of capability keywords.</p>
<p>We can use this mechanism for more complicated changes,
like introducing pipelining or removing information from
API calls.</p>
</li>
<li><p>New commands can be added; trying to use an unsupported
command will result in an error which can be checked and dealt
with.</p>
</li>
<li><p>The protocol version number can be bumped to allow graceful
refusal of old clients or servers, or to allow a client or
server to detect when it has to do things the old way.</p>
<p>This mechanism is a last resort, to be used when capability
keywords would be too hard to manage.</p>
</li>
</ol>
</li>
<li><p>Working copy and repository formats are backward- and
forward-compatible for all patch releases in the same minor
series. They are forward-compatible for all minor releases in
the same major series; however, a minor release is allowed to
make a working copy or repository that doesn't work with
previous minor releases, where "make" could mean "upgrade" as
well as "create".</p>
</li>
</ol>
<p>Subversion does not use the "even==stable, odd==unstable"
convention; any unqualified triplet indicates a stable release:</p>
<pre>
1.0.1 --&gt; first stable patch release of 1.0
1.1.0 --&gt; next stable minor release of 1.x after 1.0.x
1.1.1 --&gt; first stable patch release of 1.1.x
1.1.2 --&gt; second stable patch release of 1.1.x
1.2.0 --&gt; next stable minor release after that
</pre>
<p>The order of releases is semi-nonlinear&nbsp;&mdash;&nbsp;a 1.0.3
*might* come out after a 1.1.0. But it's only "semi"-nonlinear
because eventually we declare a patch line defunct and tell people to
upgrade to the next minor release, so over the long run the numbering
is basically linear.</p>
<p>Non-stable releases are qualified with "alphaN" or "betaN"
suffixes, and release candidates with "-rcN". For example, the
prereleases leading to 1.3.7 might look like this:</p>
<pre>
subversion-1.3.7-rc1.tar.gz
subversion-1.3.7-rc2.tar.gz
subversion-1.3.7-rc3.tar.gz
subversion-1.3.7.tar.gz
</pre>
<p>The output of 'svn --version' corresponds in the obvious way:</p>
<pre>
version 1.3.7 (Release Candidate 1)
version 1.3.7 (Release Candidate 2)
version 1.3.7 (Release Candidate 3)
version 1.3.7
</pre>
<p>When you 'make install' subversion-1.3.7-rc1, it still installs as
though it were "1.3.7", of course. The qualifiers are metadata on the
release; we want each subsequent prerelease release to overwrite the
previous one, and the final release to overwrite the last
prerelease.</p>
<p>For working copy builds, there is no tarball name to worry about,
but 'svn --version' still produces special output:</p>
<pre>
version 1.3.7 (dev build)
</pre>
<p>The version number is the next version that the development was
working towards. The important thing is to say "dev build". This
indicates that the build came from a working copy, which is useful in
bug reports.</p>
<p>We have no mechanism for releasing dated snapshots. If we want
code to get wider distribution than just those who build from working
copies, we put out a prerelease.</p>
<div class="h3" id="name-reuse" title="name-reuse">
<h3>Reuse of release names</h3>
<p>If a release or candidate release needs to be quickly re-issued due
to some non-code problem (say, a packaging glitch), it's okay to reuse
the same name, as long as the tarball hasn't been
<a href="#tarball-signing">blessed by signing</a> yet. But if it has
been uploaded to the standard distribution area with signatures, or if
the re-issue was due to a change in code a user might run, then the
old name must be tossed and the next name used.</p>
</div>
<div class="h3" id="deprecation" title="deprecation">
<h3>Deprecation</h3>
<p>When a new, improved version of an API is introduced, the old one
remains for compatibility, at least until the next major release.
However, we mark the old one as deprecated and point to the new one,
so people know to write to the new API if at all possible. When
deprecating, mention the release after which the deprecation was
introduced, and point to the new API. If possible, replace the old
API documentation with a diff to the new one. For example:</p>
<pre>
/**
* @deprecated Provided for backward compatibility with the 1.0.0 API.
*
* Similar to svn_repos_dump_fs2(), but with the @a use_deltas
* parameter always set to @c FALSE.
*/
svn_error_t *svn_repos_dump_fs(svn_repos_t *repos,
svn_stream_t *dumpstream,
svn_stream_t *feedback_stream,
svn_revnum_t start_rev,
svn_revnum_t end_rev,
svn_boolean_t incremental,
svn_cancel_func_t cancel_func,
void *cancel_baton,
apr_pool_t *pool);
</pre>
<p>When the major release number changes, the "best" new API in a
series generally replaces all the previous ones (assuming it subsumes
their functionality), and it will take the name of the original API.
Thus, marking 'svn_repos_dump_fs' as deprecated in 1.1.x doesn't mean
that 2.0.0 doesn't have 'svn_repos_dump_fs', it just means the
function's signature will be different: it will have the signature
held by svn_repos_dump_fs2 (or svn_repos_dump_fs3, or whatever) in
1.1.x. The numbered-suffix names disappear, and there is a single
(shiny, new) svn_repos_dump_fs again.</p>
<p>One exception to this replacement strategy is when the old function
has a totally unsatisfying name anyway. Deprecation is a chance to
fix that: we give the new API a totally new name, mark the old API as
deprecated, point to the new API; then at the major version change, we
remove the old API, but don't rename the new one to the old name,
because its new name is fine.</p>
</div>
</div>
<div class="h2" id="release-stabilization" title="release-stabilization">
<h2>Stabilizing and maintaining releases</h2>
<p>Minor and major number releases go through a stabilization period
before release, and remain in maintenance (bugfix) mode after release.
To start the release process, we create an "A.B.x" branch based on the
latest trunk, for example:</p>
<pre>
$ svn cp http://svn.collab.net/repos/svn/trunk \
http://svn.collab.net/repos/svn/branches/A.B.x
</pre>
<p>The stabilization period for a new A.B.0 release normally lasts
four weeks, and allows us to make conservative bugfixes and discover
showstopper issues. The stabilization period begins with a release
candidate tarball with the version A.B.0-rc1. Further release
candidate tarballs may be made as blocking bugs are fixed; for
example, if a set of language bindings is found to be broken, it is
prudent to make a new release candidate when they are fixed so that
those language bindings may be tested.</p>
<p>At the beginning of the final week of the stabilization period, a
new release candidate tarball should be made if there are any changes
pending since the last one. The final week of the stabilization
period is reserved for critical bugfixes; fixes for minor bugs should
be deferred to the A.B.1 release. A critical bug is a non-edge-case
crash, a data corruption problem, a major security hole, or something
equally serious.</p>
<p>Under some circumstances, the stabilization period will be
extended:</p>
<ul>
<li><p>If a potentially destabilizing change must be made in order to
fix a bug, the entire four-week stabilization period is
restarted. A potentially destabilizing change is one which
could affect many parts of Subversion in unpredictable ways, or
which involves adding a substantial amount of new code. Any
incompatible API change (only allowable in the first place if
the new release is an A.0.0 release) should be considered a
potentially destabilizing change.</p>
</li>
<li><p>If a critical bugfix is made during the final week of the
stabilization period, the final week is restarted. The final
A.B.0 release is always identical to the release candidate made
one week before (with the exceptions discussed below).</p>
</li>
</ul>
<p>If there are disagreements over whether a change is potentially
destabilizing or over whether a bug is critical, they may be settled
with a committer vote.</p>
<p>After the A.B.0 release is out, patch releases (A.B.1, A.B.2, etc.)
follow when bugfixes warrant them. Patch releases do not require a
four week soak, because only conservative changes go into the
line.</p>
<p>Certain kinds of commits can go into A.B.0 without restarting the
soak period, or into a later release without affecting the testing
schedule or release date:</p>
<ul>
<li><p>Without voting:</p>
<ul>
<li><p>Changes to the STATUS file.</p></li>
<li><p>Documentation file changes, including to the book, README,
INSTALL, www/, etc.</p></li>
<li><p>Changes that are a normal part of release bookkeeping, for
example, the steps listed in notes/releases.txt.</p></li>
<li><p>Changes to dist.sh by, or approved by, the release manager.</p></li>
<li><p>Changes to message translations in .po files or additions of
new .po files.</p></li>
</ul>
</li>
<li><p>With voting:</p>
<ul>
<li><p>Anything affecting only tools/, packages/, or bindings/.</p></li>
<li><p>Doc fixes in core code header or source files.</p></li>
<li><p>Changes to printed output, such as error and usage messages, as
long as format string "%" codes and their args are not
touched.</p></li>
</ul>
</li>
</ul>
<p>NOTE: The requirements on message translation changes are looser
than for text messages in C code. Changing format specifiers in .po
files is allowed because their validity can be checked mechanically
(with the -c flag on msgfmt of GNU gettext). This is done at build
time if GNU gettext is in use.</p>
<p>Core code changes, of course, require voting, and restart the soak
or test period, since otherwise the change could be undertested.</p>
<p>The voting system works like this:</p>
<p>A change to the A.B.x line must be first proposed in the
A.B.x/STATUS file. Each proposal consists of a short identifying
block (e.g., the revision number of a trunk or related-line commit, or
perhaps an issue number), a brief description of the change, an
at-most-one-line justification of why it should be in A.B.x, perhaps
some notes/concerns, and finally the votes. The notes and concerns
are meant to be brief summaries to help a reader get oriented; please
don't use the STATUS file for actual discussion, use dev@ instead.</p>
<p>Here's an example, probably as complex as an entry would ever
get:</p>
<pre>
* r98765 (issue #56789)
Make commit editor take a closure object for future mindreading.
Justification: API stability, as prep for future enhancement.
Notes: There was consensus on the desirability of this feature in
the near future; see thread at http://... (Message-Id: blahblah).
Concerns: Vetoed by jerenkrantz due to privacy concerns with the
implementation; see thread at http://... (Message-Id: blahblah)
Votes:
+1: ghudson, bliss
+0: cmpilato
-0: gstein
-1: jerenkrantz
</pre>
<p>A change needs three +1 votes from full committers (or partial
committers for the involved areas), and no vetoes, to go into
A.B.x.</p>
<p>If you cast a veto (i.e. -1), please state the reason in the
concerns field, and include a url / message-id for the list discussion
if any. You can go back and add the link later if the thread isn't
available at the time you commit the veto.</p>
<p>Voting +1 on a change doesn't just mean you approve of it in
principle. It means you have thoroughly reviewed the change, and find
it correct and as nondisruptive as possible. When it is committed to
the release branch, the log message will include the names of all who
voted for it, as well as the original author and the person making the
commit. All of these people are considered equally answerable for
bugs.</p>
<p>If you've reviewed a patch, and like it but have some reservations,
you can write "+1 (concept)" and then ask questions on the list about
your concerns. You can write "+0" if you like the general idea but
haven't reviewed the patch carefully. Neither of these votes counts
toward the total, but they can be useful for tracking down people who
are following the change and might be willing to spend more time on
it.</p>
<p>There is a somewhat looser voting system for areas that are not
core code, and that may have fewer experts available to review changes
(for example, tools/, packages/, bindings/, test scripts, etc.). A
change in these areas can go in with a +1 from a full committer or a
partial committer for that area, at least one +0 or "concept +1" from
any other committer, and no vetoes. (If a change affects the build
system, however, it is considered a core change, and needs three
+1's.) Use your judgment and don't review changes unless you have
some competence to do so, of course. The goal is to get at least two
pairs of eyes on the change, without demanding that every reviewer
have the same amount of expertise as the area maintainer. This way
one can review for general sanity, accurate comments, obvious
mistakes, etc, without being forced to assert "Yes, I understand these
changes in every detail and have tested them."</p>
<p>Before proposing a change in STATUS, you should try merging it onto
the branch to ensure that it doesn't produce merge conflicts. If
conflicts occur, please create a new temporary branch from the release
branch with your changed merged and the conflicts resolved. The
branch should be named A.B.x-rYYYY, where YYYY is the first revision
of your change in the STATUS file. Add a note in the STATUS file
about the existence of the temporary branch. If the change involves
further work, you can merge those revisions to the branch. When the
entry for this change is removed from STATUS, this temporary branch
should also be removed to avoid cluttering the /branches
directory.</p>
<p>NOTE: Changes to STATUS regarding the temporary branch, including
voting, are always kept on the main release branch.</p>
</div>
<div class="h2" id="tarball-signing">
<h2>Signing source distribution packages (a.k.a tarballs)</h2>
<p>Before a release or release candidate is officially made public, it is
made available in a temporary location for committers to test and sign.
The point is to have the tarballs tested on more systems than just that of the
person who rolled the release. When there are three signatures from full
committers for each of the <tt>.tar.bz2</tt>, <tt>.tar.gz</tt> and
<tt>.zip</tt> files, the release (candidate) can go public.</p>
<p>Signing a tarball means that you assert certain things about it. When
sending your signature (see below), indicate in the mail what steps
you've taken to verify that the tarball is correct. Running
<tt>make check</tt> over all RA layers and FS backends is a good idea,
as well as building and testing the bindings.</p>
<p>After having extracted and tested the tarball, you should sign it using
<a href="http://www.gnupg.org">gpg</a>. To do so, use a command like:</p>
<pre>
gpg -ba subversion-1.3.0-rc4.tar.bz2
</pre>
<p>This will result in a file with the same name as the signed file, but with
a <tt>.asc</tt> extension in the appropriate format for inclusion in the
release announcement. Include this file in a mail, typically in reply
to the announcement of the unofficial tarball.</p>
<p>If you've downloaded and tested a <tt>.tar.bz2</tt> file, it is possible to
sign a <tt>.tar.gz</tt> file with the same contents without having
to download and test it separately. The trick is to extract the
<tt>.bz2</tt> file, and pack it using <tt>gzip</tt> like this:</p>
<pre>
bzip2 -cd subversion-1.3.0-rc4.tar.bz2 \
| gzip -9n > subversion-1.3.0-rc4.tar.gz
</pre>
<p>The resulting file should be identical to the file generated by the
release manager, and thus can be signed as described above.
To verify that the files are identical, you may use either the MD5 checksums
or the release manager's signature, both of which should be provided with the
tarballs.
</p>
</div>
<div class="h2" id="l10n" title="l10n">
<h2>Localization (l10n)</h2>
<p>Translation has been divided into two domains. First, there is the
translation of server messages sent to connecting clients. This issue
has been <a
href="http://svn.collab.net/repos/svn/trunk/notes/l10n-problems">punted
for now</a>. Second there is the translation of the client and its
libraries.</p>
<p>The gettext package provides services for translating messages. It
uses the xgettext tool to extract strings from the sources for
translation. This works by extracting the arguments of the _() and
N_() macros. The former is used in context where function calls are
allowed (typically anything except static initializers). The latter
is used whenever _() isn't. Strings marked with N_() need to be
passed to gettext translation routines whenever referenced in the
code. For an example, look at how the header and footer are handled
in subversion/svn/help-cmd.c.</p>
<p>When using direct calls to gettext routines (*gettext or
*dgettext), keep in mind that most of Subversion code is library code.
Therefore the default domain is not necessarily Subversion's own
domain. In library code you should use the dgettext versions of the
gettext functions. The domain name is defined in the PACKAGE_NAME
define.</p>
<p>All required setup for localization is controlled by the ENABLE_NLS
conditional in svn_private_config.h (for *nix) and
svn_private_config.hw (for Windows). Be sure to put</p>
<pre>
#include "svn_private_config.h"
</pre>
<p>as the last include in any file which requires localization.</p>
<p>Also note that return values of _() and *gettext() calls are UTF-8
encoded; this means that they should be translated to the current
locale being written as any form of program output.</p>
<p>The GNU gettext manual
(<a
href="http://www.gnu.org/software/gettext/manual/html_node/gettext_toc.html"
>http://www.gnu.org/software/gettext/manual/html_node/gettext_toc.html</a>)
provides additional information on writing translatable programs in
its section "Preparing Program Sources". Its hints mainly apply to
string composition.</p>
</div>
</div>
</body>
</html>