RFR: vcs: improve git->hg converter [v2]

[Erik Helin]

> Hi all,
> 
> please review this patch that significantly improves the `GitToHgConverter`. The new converter handles all OpenJDK Git
> repositories and also handles additional Git tags. I also improved the testing by quite a bit, the verification is much
> more strict and I added a bunch of more tests. I also added some `@Disabled` tests (since they require an internet
> connection), but they are still useful for running locally when working on the converter.  Testing:
> - [x] `make test` passes on Linux x64
> - [x] Added a number of new unit tests
> 
> Thanks,
> Erik

Erik Helin has updated the pull request incrementally with one additional commit since the last revision:

  Remove debug println

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

Changes:
  - all: https://git.openjdk.java.net/skara/pull/736/files
  - new: https://git.openjdk.java.net/skara/pull/736/files/b957495a..28a0f36c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=736&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=736&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/736.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/736/head:pull/736

PR: https://git.openjdk.java.net/skara/pull/736