src/site/markdown/how-to.md

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## Overview

Cache configuration provides you additional control over incremental Maven behavior. Follow it step by step to
understand how it works and figure out your optimal config

### Minimal config

Absolutely minimal config

```xml
<?xml version="1.0" encoding="UTF-8" ?>
<cache xmlns="http://maven.apache.org/BUILD-CACHE-CONFIG/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://maven.apache.org/BUILD-CACHE-CONFIG/1.0.0 http://maven.apache.org/xsd/cache-config-1.0.0.xsd">

    <configuration>
        <enabled>true</enabled>
        <hashAlgorithm>XX</hashAlgorithm>
    </configuration>

    <input>
        <global>
            <glob>{*.java,*.xml,*.properties}</glob>
        </global>
    </input>
</cache>
```

### Enabling remote cache

Just add `<remote>` section under `<configuration>`

```xml
    <configuration>
        <enabled>true</enabled>
        <hashAlgorithm>XX</hashAlgorithm>
        <remote>
            <url>https://yourserver:port</url>
        </remote>
    </configuration>
```

### Adding more file types to input

Add all the project specific source code files in `<glob>`. Scala in this case:

```xml
    <input>
        <global>
            <glob>{*.java,*.xml,*.properties,*.scala}</glob>
        </global>
    </input>
```

### Adding source directory for bespoke project layouts

In most of the cases incremental Maven will recognize directories automatically by build introspection. If not, you can
add additional directories with `<include>`. Also you can filter out undesirable dirs and files by using exclude tag

```xml
    <input>
        <global>
            <glob>{*.java,*.xml,*.properties,*.scala}</glob>
            <includes>
                <include>importantdir/</include>
            </includes>
            <excludes>
                <exclude>tempfile.out</exclude>
            </excludes>
        </global>
    </input>
```

### Plugin property is env specific and yields different cache key in different environments

Consider to exclude env specific properties:

```xml
    <input>
        <global>
            ...
        </global>
        <plugins>
            <plugin artifactId="maven-surefire-plugin">
                <effectivePom>
                    <excludeProperties>
                        <excludeProperty>argLine</excludeProperty>
                    </excludeProperties>
                </effectivePom>
            </plugin>
        </plugins>
    </input>
```

Implications - builds with different `argLine` will have identical key. Validate that is semantically valid.

### Plugin property points to directory where only subset of files is relevant

If plugin configuration property points to `somedir` it will be scanned with default glob. You can tweak it with custom
processing rule

```xml
    <input>
        <global>
            ...
        </global>
        <plugins>
            <plugin artifactId="protoc-maven-plugin">
                <dirScan mode="auto">
                    <!--<protoBaseDirectory>${basedir}/..</protoBaseDirectory>-->
                    <tagScanConfigs>
                        <tagScanConfig tagName="protoBaseDirectory" recursive="false" glob="{*.proto}"/>
                    </tagScanConfigs>
                </dirScan>
            </plugin>
        </plugins>
    </input>
```

### Local repository is not updated because `install` is cached

Add `executionControl/runAlways` section

```xml
    <executionControl>
        <runAlways>
            <plugins>
                <plugin artifactId="maven-failsafe-plugin"/>
            </plugins>
            <executions>
                <execution artifactId="maven-dependency-plugin">
                    <execIds>
                        <execId>unpack-autoupdate</execId>
                    </execIds>
                </execution>
            </executions>
            <goalsLists>
                <goalsList artifactId="maven-install-plugin">
                    <goals>
                        <goal>install</goal>
                    </goals>
                </goalsList>
            </goalsLists>
        </runAlways>
    </executionControl>
```

### I occasionally cached build with `-DskipTests=true` and tests do not run now

If you add command line flags to your build, they do not participate in effective pom - Maven defers final value
resolution to plugin runtime. To invalidate build if filed value is different in runtime, add reconciliation section
to `executionControl`:

```xml
<?xml version="1.0" encoding="UTF-8" ?>
<cache xmlns="http://maven.apache.org/CACHE-CONFIG/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://maven.apache.org/CACHE-CONFIG/1.0.0 http://maven.apache.org/xsd/cache-config-1.0.0.xsd">
    <configuration>
        ...
    </configuration>
    <executionControl>
        <runAlways>
            ...
        </runAlways>
        <reconcile>
            <plugins>
                <plugin artifactId="maven-surefire-plugin" goal="test">
                    <reconciles>
                        <reconcile propertyName="skip" skipValue="true"/>
                        <reconcile propertyName="skipExec" skipValue="true"/>
                        <reconcile propertyName="skipTests" skipValue="true"/>
                        <reconcile propertyName="testFailureIgnore" skipValue="true"/>
                    </reconciles>
                </plugin>
            </plugins>
        </reconcile>
    </executionControl>
</cache>
```

Please notice `skipValue` attribute. It denotes value which forces skipped execution.
Read `propertyName="skipTests" skipValue="true"` as if property skipTests has value true, plugin will skip execution If
you declare such value incremental Maven will reuse appropriate full-build though technically they are different, but
because full-build is better it is safe to reuse

### How to renormalize line endings in working copy after committing .gitattributes (git 2.16+)

Ensure you've committed (and ideally pushed everything) - no changes in working copy. After that:

```shell
# Rewrite objects and update index
git add --renormalize .
# Commit changes
git commit -m "Normalizing line endings"
# Remove working copy paths from git cache
git rm --cached -r .
# Refresh with new line endings
git reset --hard
```

### I want to cache interim build and override it later with final version

Solution: set `-Dmaven.build.cache.remote.save.final=true` to nodes which produce final builds. Such builds will not be overridden
and eventually will replace all interim builds