* FileTreeIteratorTest: Open Git and RevWalk in try-with-resource
* RebaseCommandTest: Open RevWalk in try-with-resource
* PullCommandTest: Open RevWalk in try-with-resource
* BlameGeneratorTest: Create Git instances in try-with-resource
* Remove unnecessary suppression of deprecation warnings in tests
* DiffEntryTest: Open Git and TreeWalk in try-with-resource
* DiffCommandTest: Open Git and RevWalk in try-with-resource
* CommitCommandTest: Open Git and TreeWalk in try-with-resource
* Cosmetic adjustment of relative date format, do not display "0 months"
* Make use of the many date formatting options in the log command
* Define a utility class for handling Git date formats