Merge branch 'cc/cherry-pick-ff'

* cc/cherry-pick-ff:
  revert: fix tiny memory leak in cherry-pick --ff
  rebase -i: use new --ff cherry-pick option
  Documentation: describe new cherry-pick --ff option
  cherry-pick: add tests for new --ff option
  revert: add --ff option to allow fast forward when cherry-picking
  builtin/merge: make checkout_fast_forward() non static
  parse-options: add parse_options_concat() to concat options

builtin/merge.c

@@ -667,7 +667,7 @@ static int count_unmerged_entries(void)
 	return ret;
 }
 
-static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
+int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 {
 	struct tree *trees[MAX_UNPACK_TREES];
 	struct unpack_trees_options opts;