Maven release plugin on a multi-module project having different releasecycles and hence versions

With Git migration headed in our direction, we were testing the readiness of our utility scripts for this new SCM. The maven-release-plugin had advertised that it supports git as a SCM and we were hoping that it would be straight-forward.

The project structure was like

• parent




• child1


• child2


• child3

We modified the parent pom file of parent as

    <scm>
        <connection>scm:git:ssh://gitserve/test/parent.git</connection>
        <developerConnection>scm:git:ssh://gitserve/test/parent.git</developerConnection>
        <url>http://gitweb/?p=test/parent.git;a=summary</url>
    </scm>

FTR, the connection tag is the read link and the developerConnection is the read-write link. This is supported for cases where one may allow the reads and writes to happen via different transports - say HTTP for reads and only SSH for writes.

Also, the maven-release-plugin v 2.3.2 fixes some significant bugs, so make sure that you use this version of the plugin. Best set it up via pluginManagement.

We follow the standard pattern of moving changes from trunk -> branch -> tag in the SVN world.
With the move to Git, the tag is a real tag and is really a read-only point in the history of the project and hence no need to have commit hooks that were added to support the notion on tags in the SVN world. Other open source projects like Spring, Sonatype have adopted a similar approach.

Now comes the interesting part of doing a minor release for one of the sub-modules - say child2. With the regular invocation of the maven release:branch, it was complaining of an invalid git location as

ssh://gitserve/test/parent.git/child2

Clearly, this was not a valid git location. I finally stumbled on this SO question which discusses that this is actually some intelligence on the part of the maven release plugin when it encounters multiple projects. So, the workaround? We just need to redefine the scm tags in the individual sub-modules again and voila - you are done!

Yes, this was a long winding rant, but hopefully someone will benefit from it!