[JENKINS-60590] Fix AbstractGitSCMSource.retrieve repository leak

[slonopotamus]

JENKINS-60590 Fix repository leak

This bug is detected by AbstractGitSCMSourceTest.when_commits_added_during_discovery_we_do_not_crash to if run against newer JTH.

Checklist

• I have read the CONTRIBUTING doc
• Tests verify my changes
• Unit tests pass locally with my changes
• I have added documentation as necessary
• No Javadoc warnings were introduced with my changes
• No spotbugs warnings were introduced with my changes
• Any dependent changes have been merged and published in upstream modules (like git-client-plugin)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

[oleg-nenashev]

Thanks, nice fix!

[basil]

Does a similar bug exist further down in the same file, on lines 954–955:

git-plugin/src/main/java/jenkins/plugins/git/AbstractGitSCMSource.java

Lines 954 to 955 in 2ed80a1

	final Repository repository = client.getRepository();
	try (RevWalk walk = new RevWalk(repository)) {

[MarkEWaite]

Yes @basil that is the same problem in a different location. Thanks for detecting it!