RFR: git-pr: do not assume a master branch

[Robin Westberg]

On Fri, 7 Feb 2020 15:21:25 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that makes `git pr` work even though no `master` branch
> is present (which is the case if you clone a repository that uses a different
> default branch). The fix consists of two parts:
> 
> - Use a better algorithm for detecting the target branch. `git pr create` will
>   now pick the "closest" branch that exists in the upstream (parent) repository
>   as the target branch by default.
> - Read the .jcheck/conf file from the target branch
> 
> Testing:
> - Manually tested `git pr create` on different repositories on Linux x64
> 
> Thanks,
> Erik

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/415