MNG-6759: Fix issue where MavenMetadataSource failed to set the right…

[srdo]

… repositories when preparing artifact metadata

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Please see the issue description at https://issues.apache.org/jira/browse/MNG-6759. The basic issue is that when there's a dependency graph like A -> B -> C, and C is in some non-Central repository listed by B's POM, Maven is supposed to look for it in the repositories listed by B. As of 3.6.2, this doesn't always happen.

The issue is caused by an oversight in d3ace78. When the optimization is triggered, the "pomRepositories" variable is not set. In the slow path, it will be set to the remoteRepositories of the parent artifact in the dependency trail.

I'd like advice on improving this fix, as I'm using a deprecated method which is probably not a good idea. The optimized path gets the Model of the artifact. I need a list of ArtifactRepository, but the Model only contains a list of Repository. Should I use a RepositorySystem to map them? It feels like a waste, as they already exist in the session's set of MavenProject. I'd get them from the ReactorReader, but it unfortunately only exposes the Model.

[srdo]

There's another issue related to this one, which is also introduced in the linked commit. I don't know if it's a big deal. Would appreciate if someone more familiar with Maven would consider it.

When the optimized path is hit, the relocatedArtifact variable at https://github.com/apache/maven/pull/294/files#diff-e24970dce03124cc7d88af538539cf07R181 does not get set. I'm uncertain what kind of impact this may have.