RFR: 295: jcheck should always use configuration from the target branch

[Robin Westberg]

On Wed, 4 Mar 2020 10:20:05 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that ensures that the bots always use the .jcheck/conf
> from the target branch when checking pull requests.
> 
> Testing:
> - `make test` passes on Linux x64
> - Added a few new unit tests
> 
> Thanks,
> Erik

Looks good, we can skip some rebasing done by the bots as well, but that can be fixed later.

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/491