Merge branch 'cc/revert-strategy'

Merge branch 'cc/revert-strategy'

* cc/revert-strategy:
  revert: add "--strategy" option to choose merge strategy
  merge: make function try_merge_command non static
  merge: refactor code that calls "git merge-STRATEGY"
  revert: refactor merge recursive code into its own function
  revert: use strbuf to refactor the code that writes the merge message

Conflicts:
	builtin/revert.c