Support explicit merging of tiles plugin configuration

[lfvJonas]

We have just started to integrate tiles in our projects but we have found some issues when we trying split plugin configuration into diffrent tiles.

As stated in the README.md if there are overlapping configuration options only the closes tile gets picked and the other gets ignored.

It would be nice if we could configure the behaviour of Maven Tiles to merge these overlapping plugin configuration options instead of ignoring them.

In #101 a simular behaivour is achived but only for execution configurations. Though it is a little combersome to use, a single configuration option <merge-plugin-configuration>true</merge-plugin-configuration> in the consuming tile/applicaiton would be Ideal.

Here is an examle:

Tile 1 (tile.xml)

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <build>
        <plugins>
            <plugin>
                <groupId>org.eclipse.m2e</groupId>
                <artifactId>lifecycle-mapping</artifactId>
                <version>1.0.0</version>
                <configuration>
                    <lifecycleMappingMetadata>
                        <pluginExecutions>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>org.apache.maven.plugins</groupId>
                                    <artifactId>maven-dependency-plugin</artifactId>
                                    <versionRange>[3.3.0,)</versionRange>
                                    <goals>
                                        <goal>unpack</goal>
                                    </goals>
                                </pluginExecutionFilter>
                                <action>
                                    <ignore />
                                </action>
                            </pluginExecution>
                        </pluginExecutions>
                    </lifecycleMappingMetadata>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Tile 2 (tile.xml)

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <build>
        <plugins>
            <plugin>
                <groupId>org.eclipse.m2e</groupId>
                <artifactId>lifecycle-mapping</artifactId>
                <version>1.0.0</version>
                <configuration>
                    <lifecycleMappingMetadata>
                        <pluginExecutions>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>org.cyclonedx</groupId>
                                    <artifactId>cyclonedx-maven-plugin</artifactId>
                                    <versionRange>[2.7.3,)</versionRange>
                                    <goals>
                                        <goal>makeAggregateBom</goal>
                                    </goals>
                                </pluginExecutionFilter>
                                <action>
                                    <ignore />
                                </action>
                            </pluginExecution>
                        </pluginExecutions>
                    </lifecycleMappingMetadata>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Application (pom.xml)

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.test</groupId>
    <artifactId>application</artifactId>
    <version>0.1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <build>
        <plugins>
            <plugin>
                <groupId>io.repaint.maven</groupId>
                <artifactId>tiles-maven-plugin</artifactId>
                <version>2.38</version>
                <extensions>true</extensions>
                <configuration>
                    <filtering>false</filtering>
                    <tiles>
                        <tile>com.test:tile-1:0.1.0-SNAPSHOT</tile>
                        <tile>com.test:tile-2:0.1.0-SNAPSHOT</tile>
                    </tiles>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Effective pom (Current behaviour)

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <build>
        <plugins>
            <plugin>
                <groupId>org.eclipse.m2e</groupId>
                <artifactId>lifecycle-mapping</artifactId>
                <version>1.0.0</version>
                <configuration>
                    <lifecycleMappingMetadata>
                        <pluginExecutions>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>org.apache.maven.plugins</groupId>
                                    <artifactId>maven-dependency-plugin</artifactId>
                                    <versionRange>[3.3.0,)</versionRange>
                                    <goals>
                                        <goal>unpack</goal>
                                    </goals>
                                </pluginExecutionFilter>
                                <action>
                                    <ignore />
                                </action>
                            </pluginExecution>
                        </pluginExecutions>
                    </lifecycleMappingMetadata>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Effective pom (Wanted behaviour)

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <build>
        <plugins>
            <plugin>
                <groupId>org.eclipse.m2e</groupId>
                <artifactId>lifecycle-mapping</artifactId>
                <version>1.0.0</version>
                <configuration>
                    <lifecycleMappingMetadata>
                        <pluginExecutions>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>org.apache.maven.plugins</groupId>
                                    <artifactId>maven-dependency-plugin</artifactId>
                                    <versionRange>[3.3.0,)</versionRange>
                                    <goals>
                                        <goal>unpack</goal>
                                    </goals>
                                </pluginExecutionFilter>
                                <action>
                                    <ignore />
                                </action>
                            </pluginExecution>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>org.cyclonedx</groupId>
                                    <artifactId>cyclonedx-maven-plugin</artifactId>
                                    <versionRange>[2.7.3,)</versionRange>
                                    <goals>
                                        <goal>makeAggregateBom</goal>
                                    </goals>
                                </pluginExecutionFilter>
                                <action>
                                    <ignore />
                                </action>
                            </pluginExecution>
                        </pluginExecutions>
                    </lifecycleMappingMetadata>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

[lfvjimisola]

I'm in the same team as @lfvJonas. We seem to have the same issue with configuration for plugins using Annotations Processors.