RFR: git-pr: move subcommands to separate files

[Robin Westberg]

On Thu, 20 Feb 2020 13:25:05 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that splits `GitPr.java` into multiple files - one file
> per sub-command. This makes the code much more maintainable and allows for easy
> addition of new commands.
> 
> Testing:
> - Manual testing of `git pr`
> 
> Thanks,
> Erik

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/460