Merge branch 'nd/merge-quit'

"git merge" learned "--quit" option that cleans up the in-progress
merge while leaving the working tree and the index still in a mess.

* nd/merge-quit:
  merge: add --quit
  merge: remove drop_save() in favor of remove_merge_branch_state()

Documentation/git-merge.txt

@@ -100,6 +100,10 @@ commit or stash your changes before running 'git merge'.
 'git merge --abort' is equivalent to 'git reset --merge' when
 `MERGE_HEAD` is present.
 
+--quit::
+	Forget about the current merge in progress. Leave the index
+	and the working tree as-is.
+
 --continue::
 	After a 'git merge' stops due to conflicts you can conclude the
 	merge by running 'git merge --continue' (see "HOW TO RESOLVE