Merge branch 'sb/merge-commit-msg-hook'

Merge branch 'sb/merge-commit-msg-hook'

As "git commit" to conclude a conflicted "git merge" honors the
commit-msg hook, "git merge" that records a merge commit that
cleanly auto-merges should, but it didn't.
* sb/merge-commit-msg-hook (2017-09-22) 1 commit
(merged to 'next' on 2017-09-25 at 096e0502a8)
+ Documentation/githooks: mention merge in commit-msg hook

Add documentation for a topic that has recently graduated to the
'master' branch.

* sb/merge-commit-msg-hook:
  Documentation/githooks: mention merge in commit-msg hook