Relative paths in pmd report result in missing code snippets

[adangel]

PMD6 reports absolute paths, PMD7 seems to report only relative paths (relative to the current working directory).

• pmd6: /home/runner/work/pmd/target/repositories/openjdk-11/src/java.base/aix/classes/sun/nio/ch/AixAsynchronousChannelProvider.java
• pmd7: target/repositories/openjdk-11/src/java.base/aix/classes/sun/nio/ch/AixAsynchronousChannelProvider.java

The regression tester should be able to deal with both situations. It will relativize the paths on its own (relative to the project root, that is /home/runner/work/pmd/target/repositories/openjdk-11).

The problem is, that we generate wrong links to the source code, e.g. https://github.com/openjdk/jdk/tree/jdk-11+28/target/repositories/openjdk-11/src/java.base/share/classes/java/util/AbstractMap.java#L609 instead of https://github.com/openjdk/jdk/tree/jdk-11+28/src/java.base/share/classes/java/util/AbstractMap.java#L609

[adangel]

Another example: comparison between master and pmd/7.0.x is also broken: https://chunk.io/pmd/239601d3404a4537945d24b60b36b275/diff2/Schedul-o-matic-9000/index.html#section-violations