cherry-pick: allow "-" as abbreviation of '@{-1}'

"-" abbreviation is handy for "cherry-pick" like "checkout" and "merge".

It's also good for uniformity that a "-" stands as
the name of the previous branch where a branch name is
accepted and it could not mean any other things like stdin.

Signed-off-by: Hiroshige Umino <hiroshige88@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/revert.c

@@ -232,6 +232,8 @@ int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 	memset(&opts, 0, sizeof(opts));
 	opts.action = REPLAY_PICK;
 	git_config(git_default_config, NULL);
+	if (!strcmp(argv[1], "-"))
+		argv[1] = "@{-1}";
 	parse_args(argc, argv, &opts);
 	res = sequencer_pick_revisions(&opts);
 	if (res < 0)