* 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