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)

t/t3501-revert-cherry-pick.sh

@@ -109,4 +109,24 @@ test_expect_success 'chery-pick on unborn branch' '
 	! test_cmp_rev initial HEAD
 '
 
+test_expect_success 'cherry-pick "-" to pick from previous branch' '
+	git checkout unborn &&
+	test_commit to-pick actual content &&
+	git checkout master &&
+	git cherry-pick - &&
+	echo content >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'cherry-pick "-" is meaningless without checkout' '
+	test_create_repo afresh &&
+	(
+		cd afresh &&
+		test_commit one &&
+		test_commit two &&
+		test_commit three &&
+		test_must_fail git cherry-pick -
+	)
+'
+
 test_done