RFR: git-pr: use upstream remote if available

[Robin Westberg]

On Thu, 5 Dec 2019 11:03:09 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this PR that updates `git pr` to make use of a `upstream` remote
> if one is available. This speeds things up a bit since we don't have use the
> forges REST API's to find the upstream ("parent") repository.
> 
> Thanks,
> Erik
> 
> - [x] Manual testing of `git-pr` on Linux x64

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/297