RFR: pr: use bare repo for CommitCommentsWorkItem

[Erik Helin]

Hi all,

please review this patch that makes `CommitCommentsWorkItem` use a bare repository and also always update the repository returned by `HostedRepositoryPool.materialize`. This will ensure that the repository is materialized a bit faster the first time and also that it is always up to date.

Thanks,
Erik

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Commit messages:
 - pr: use bare repo for CommitCommentsWorkItem

Changes: https://git.openjdk.java.net/skara/pull/1062/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1062&range=00
  Stats: 8 lines in 1 file changed: 1 ins; 4 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/1062.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1062/head:pull/1062

PR: https://git.openjdk.java.net/skara/pull/1062