Merge branch 'fc/remote-hg' into next

Merge branch 'fc/remote-hg' into next

New remote helper for hg.

* fc/remote-hg:
  remote-hg: avoid bad refs
  remote-hg: try the 'tip' if no checkout present
  remote-hg: fix compatibility with older versions of hg
  remote-hg: add missing config for basic tests
  remote-hg: the author email can be null
  remote-hg: add option to not track branches
  remote-hg: add extra author test
  remote-hg: add tests to compare with hg-git
  remote-hg: add bidirectional tests
  test-lib: avoid full path to store test results
  remote-hg: add basic tests
  remote-hg: fake bookmark when there's none
  remote-hg: add compat for hg-git author fixes
  remote-hg: add support for hg-git compat mode
  remote-hg: match hg merge behavior
  remote-hg: make sure the encoding is correct
  remote-hg: add support to push URLs
  remote-hg: add support for remote pushing
  remote-hg: add support for pushing
  Add new remote-hg transport helper