Fix incorrect inherited URLs in pom.xml

[Marcono1234]

Purpose

Fixes incorrect inherited URLs in the pom.xml, mainly in the one of the gson Maven module

Description

Previously Maven appended the artifact ID of the modules which lead for example for the gson module to the incorrect URL https://github.com/google/gson/gson (note the extra /gson at the end). This could be seen for example with mvn help:effective-pom:

...
 <url>https://github.com/google/gson/gson</url>
...
  <scm>
    <connection>scm:git:https://github.com/google/gson.git/gson</connection>
    <developerConnection>scm:git:git@github.com:google/gson.git/gson</developerConnection>
    <url>https://github.com/google/gson/gson/</url>
  </scm>
...

Other situations where this might have been visible are when using plugins to generate a summary of dependencies of a project and probably also the Sonatype Maven Central browser (see "Project URL" on the right).

This pull request uses the attributes described here to disable appending the artifact ID of the modules. With these changes the output of mvn help:effective-pom looks correct:

...
  <url>https://github.com/google/gson</url>
...
  <scm child.scm.connection.inherit.append.path="false" child.scm.developerConnection.inherit.append.path="false" child.scm.url.inherit.append.path="false">
    <connection>scm:git:https://github.com/google/gson.git</connection>
    <developerConnection>scm:git:git@github.com:google/gson.git</developerConnection>
    <url>https://github.com/google/gson/</url>
  </scm>
...

See also the related Guava issue: google/guava#5618

Checklist

• New code follows the Google Java Style Guide
• If necessary, new public API validates arguments, for example rejects null
• New public API has Javadoc
  • Javadoc uses @since $next-version$
    ($next-version$ is a special placeholder which is automatically replaced during release)
• If necessary, new unit tests have been added
  • Assertions in unit tests use Truth, see existing tests
  • No JUnit 3 features are used (such as extending class TestCase)
  • If this pull request fixes a bug, a new test was added for a situation which failed previously and is now fixed
• mvn clean verify javadoc:jar passes without errors

[eamonnmcmanus]

Thanks!