RFR: 1355: Mirror bot needs branch selection based on patterns

[Erik Joelsson]

This patch makes it possible to configure mirrored branches with regex patterns. For what I think is improved readability, I made it possible to supply the patterns as an array of strings, so we can have multiple separate patterns. It's still possible to define "branches" as a comma separated list, for backwards compatibility.

When deploying this change, I will need to delete the existing local repos used for mirroring on the bot runner machine, because the method by which repos are cloned is changing (for repos that do not just mirror "everything"). Going forward, I think it's good to always clone all repos the same way, regardless of configuration.

There is another behavioral change, where I'm adding `--force` when pushing branches with `includeTags`. It happens a bit too often that a repo maintainer changes tags, which currently causes error for any mirroring job because we aren't force pushing tags. I don't think we ever want to not force update when mirroring repos.

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Commit messages:
 - SKARA-1355

Changes: https://git.openjdk.org/skara/pull/1358/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1358&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1355
  Stats: 116 lines in 4 files changed: 88 ins; 7 del; 21 mod
  Patch: https://git.openjdk.org/skara/pull/1358.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1358/head:pull/1358

PR: https://git.openjdk.org/skara/pull/1358