fast_forward_to  2077 builtin/am.c   	if (fast_forward_to(head_tree, head_tree, 1))
fast_forward_to  2087 builtin/am.c   	if (fast_forward_to(index_tree, remote_tree, 0))
fast_forward_to   508 sequencer.c    		return fast_forward_to(commit->object.sha1, head, unborn, opts);