Use JGit 5.6.0
Use JGit 5.6.0

It contains new features & a couple of bug fixes:
- https://wiki.eclipse.org/JGit/New_and_Noteworthy/5.6
- https://projects.eclipse.org/projects/technology.jgit/releases/5.6.0

MarkEWaite/git-client-plugin,MarkEWaite/git-client-plugin,MarkEWaite/git-client-plugin