Implement new required 'version' specification in project.conf
This adds a required field to project.conf to specify the BuildStream
version required by the project, and this serves two separate purposes
at once:
A.) It is a more practical method for users to specify the format-version
The "format-version" field requires that users know about which
format version each YAML feature was added in, and this version
is separate from the BuildStream version.
As such, it is more difficult to use - the field is still
preserved and supported, but mostly only useful in order
to depend on format versions in unstable release periods.
B.) It serves to ensure that the wrong major point version
of BuildStream is never used with the wrong project.
Changes in this commit include:
* _versions.py: Added BST_API_VERION_MAJOR and BST_API_VERION_MINOR
These include comments about how the fields must be updated when
work commences on any major or minor point stable release, usually
on the master branch.
* _project.py: Support parsing the new "version"
* _frontend/app.py: The `bst init` command has been extended to also
dump the current API version automatically.
This should really be enhanced separately, but since the test cases
use `bst init` in some places in order to create projects for test
purposes, I've included the minimal change here and will enhance
`bst init` separately.
* tests: All tests updated to include a "version: 2.0" specification
in the project.conf files under test
181 files changed
