RFR: hg: use --template instead of ext.py for metadata [v3]

[Erik Helin]

> Hi all,
> 
> please review this patch that makes `HgRepository.commitMetadata` use `--template` instead of `ext.py` for generating
> the metadata.
> Testing:
> - [x] `make test` passes on Linux x64
> 
> Thanks,
> Erik

Erik Helin has updated the pull request with a new target base due to a merge or a rebase. The pull request now
contains one commit:

  hg: use --template instead of ext.py for metadata

-------------

Changes: https://git.openjdk.java.net/skara/pull/739/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=739&range=02
  Stats: 43 lines in 2 files changed: 33 ins; 3 del; 7 mod
  Patch: https://git.openjdk.java.net/skara/pull/739.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/739/head:pull/739

PR: https://git.openjdk.java.net/skara/pull/739