cherry-pick: add --allow-empty-message option

Scripts such as "git rebase -i" cannot currently cherry-pick commits
which have an empty commit message, as git cherry-pick calls git
commit without the --allow-empty-message option.

Add an --allow-empty-message option to git cherry-pick which is passed
through to git commit, so this behaviour can be overridden.

Signed-off-by: Chris Webb <chris@arachsys.com>
Reviewed-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-cherry-pick.txt

@@ -116,6 +116,11 @@ effect to your index in a row.
 	previous commit are dropped.  To force the inclusion of those commits
 	use `--keep-redundant-commits`.
 
+--allow-empty-message::
+	By default, cherry-picking a commit with an empty message will fail.
+	This option overrides that behaviour, allowing commits with empty
+	messages to be cherry picked.
+
 --keep-redundant-commits::
 	If a commit being cherry picked duplicates a commit already in the
 	current history, it will become empty.  By default these

builtin/revert.c

@@ -117,6 +117,7 @@ static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 		OPT_END(),
 		OPT_END(),
 		OPT_END(),
+		OPT_END(),
 	};
 
 	if (opts->action == REPLAY_PICK) {
@@ -124,6 +125,7 @@ static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 			OPT_BOOLEAN('x', NULL, &opts->record_origin, "append commit name"),
 			OPT_BOOLEAN(0, "ff", &opts->allow_ff, "allow fast-forward"),
 			OPT_BOOLEAN(0, "allow-empty", &opts->allow_empty, "preserve initially empty commits"),
+			OPT_BOOLEAN(0, "allow-empty-message", &opts->allow_empty_message, "allow commits with empty messages"),
 			OPT_BOOLEAN(0, "keep-redundant-commits", &opts->keep_redundant_commits, "keep redundant, empty commits"),
 			OPT_END(),
 		};

sequencer.c

@@ -311,6 +311,9 @@ static int run_git_commit(const char *defmsg, struct replay_opts *opts,
 	if (allow_empty)
 		argv_array_push(&array, "--allow-empty");
 
+	if (opts->allow_empty_message)
+		argv_array_push(&array, "--allow-empty-message");
+
 	rc = run_command_v_opt(array.argv, RUN_GIT_CMD);
 	argv_array_clear(&array);
 	return rc;

sequencer.h

@@ -30,6 +30,7 @@ struct replay_opts {
 	int allow_ff;
 	int allow_rerere_auto;
 	int allow_empty;
+	int allow_empty_message;
 	int keep_redundant_commits;
 
 	int mainline;

t/t3505-cherry-pick-empty.sh

@@ -53,6 +53,11 @@ test_expect_success 'index lockfile was removed' '
 
 '
 
+test_expect_success 'cherry-pick a commit with an empty message with --allow-empty-message' '
+	git checkout -f master &&
+	git cherry-pick --allow-empty-message empty-branch
+'
+
 test_expect_success 'cherry pick an empty non-ff commit without --allow-empty' '
 	git checkout master &&
 	echo fourth >>file2 &&