RFR: 195: git-pr should support flag --ignore-local-commits

[Erik Helin]

Hi all,

please review this patch that adds the flag `--ignore-local-commits` to `git-pr
create` (also configurable). If `--ignore-local-commits` is specified then
`git-pr create` will not complain about local commits in the branch have not
been pushed.

Thanks,
Erik

- [x] Manual testing of `git-pr create`

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Commits:
 - 2234680f: skara-195

Changes: https://git.openjdk.java.net/skara/pull/320/files
 Webrev: https://webrevs.openjdk.java.net/skara/320/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-195
  Stats: 34 lines in 1 file changed: 18 ins; 6 del; 10 mod
  Patch: https://git.openjdk.java.net/skara/pull/320.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/320/head:pull/320

PR: https://git.openjdk.java.net/skara/pull/320