Merge branch 'jn/merge-diff3-label'

Merge branch 'jn/merge-diff3-label'

* jn/merge-diff3-label:
  merge-recursive: add a label for ancestor
  cherry-pick, revert: add a label for ancestor
  revert: clarify label on conflict hunks
  compat: add mempcpy()
  checkout -m --conflict=diff3: add a label for ancestor
  merge_trees(): add ancestor label parameter for diff3-style output
  merge_file(): add comment explaining behavior wrt conflict style
  checkout --conflict=diff3: add a label for ancestor
  ll_merge(): add ancestor label parameter for diff3-style output
  merge-file --diff3: add a label for ancestor
  xdl_merge(): move file1 and file2 labels to xmparam structure
  xdl_merge(): add optional ancestor label to diff3-style output
  tests: document cherry-pick behavior in face of conflicts
  tests: document format of conflicts from checkout -m

Conflicts:
	builtin/revert.c