RFR: merge-bot: give each branch a new number as name

[Robin Westberg]

On Wed, 15 Apr 2020 09:26:51 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that makes the merge bot always increment its branch
> names by one. The previous code (mistakenly) used the number of open pull
> request, but that is not monotonically increasing. Since the merge bot does not
> delete branches it has created, the number of branches should be monotonically
> increasing ��
> 
> Testing:
> - `make test` on Linux x64 passes
> 
> Thanks,
> Erik

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/579