[PATCH v4 3/6] commit: add a reword suboption to --fixup

[Charvi Mendiratta <charvi077@gmail.com>]

`git commit --fixup=reword:<commit>` aliases
`--fixup=amend:<commit> --only`, where it creates an empty "amend!"
commit that will reword <commit> without changing its contents when
it is rebased with `--autosquash`.

Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Mentored-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Charvi Mendiratta <charvi077@gmail.com>
---
 builtin/commit.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 05594fa8ab..d8cec75888 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1188,6 +1188,19 @@ static void finalize_deferred_config(struct wt_status *s)
 		s->ahead_behind_flags = AHEAD_BEHIND_FULL;
 }
 
+static void check_fixup_reword_options(int argc, const char *argv[]) {
+	if (whence != FROM_COMMIT) {
+		if (whence == FROM_MERGE)
+			die(_("You are in the middle of a merge -- cannot reword."));
+		else if (is_from_cherry_pick(whence))
+			die(_("You are in the middle of a cherry-pick -- cannot reword."));
+	}
+	if (argc)
+		die(_("cannot combine reword option of --fixup with path '%s'"), *argv);
+	if (patch_interactive || interactive || all || also || only)
+		die(_("reword option of --fixup is mutually exclusive with --patch/--interactive/--all/--include/--only"));
+}
+
 /* returns the length of intial segment of alpha characters only */
 static size_t get_alpha_len(char *fixup_message) {
 	const char alphas[] = "abcdefghijklmnopqrstuvwxyz";
@@ -1276,17 +1289,22 @@ static int parse_and_validate_options(int argc, const char *argv[],
 		 * reference for example: --fixup="HEAD^{/^area: string}" or
 		 * a suboption of `--fixup`.
 		 *
-		 * As `amend` suboption contains only alpha character.
-		 * So check if first non alpha character in fixup_message
-		 * is ':'.
+		 * As `amend`/`reword` suboptions contains only alpha
+		 * characters. So check if first non alpha character
+		 * in fixup_message is ':'.
 		 */
 		size_t len = get_alpha_len(fixup_message);
 		if (len && fixup_message[len] == ':') {
 			fixup_message[len++] = '\0';
 			fixup_commit = fixup_message + len;
-			if (!strcmp("amend", fixup_message)) {
+			if (!strcmp("amend", fixup_message) ||
+			    !strcmp("reword", fixup_message)) {
 				fixup_prefix = "amend";
 				allow_empty = 1;
+				if (*fixup_message == 'r') {
+					check_fixup_reword_options(argc, argv);
+					only = 1;
+				}
 			} else {
 				die(_("unknown option: --fixup=%s:%s"), fixup_message, fixup_commit);
 			}
@@ -1575,10 +1593,10 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		OPT_STRING('c', "reedit-message", &edit_message, N_("commit"), N_("reuse and edit message from specified commit")),
 		OPT_STRING('C', "reuse-message", &use_message, N_("commit"), N_("reuse message from specified commit")),
 		/*
-		 * TRANSLATORS: Leave "[amend:]" as-is, and
-		 * only translate <commit>.
+		 * TRANSLATORS: Leave "[(amend|reword):]" as-is,
+		 * and only translate <commit>.
 		 */
-		OPT_STRING(0, "fixup", &fixup_message, N_("[amend:]commit"), N_("use autosquash formatted message to fixup or amend specified commit")),
+		OPT_STRING(0, "fixup", &fixup_message, N_("[(amend|reword):]commit"), N_("use autosquash formatted message to fixup or amend/reword specified commit")),
 		OPT_STRING(0, "squash", &squash_message, N_("commit"), N_("use autosquash formatted message to squash specified commit")),
 		OPT_BOOL(0, "reset-author", &renew_authorship, N_("the commit is authored by me now (used with -C/-c/--amend)")),
 		OPT_BOOL('s', "signoff", &signoff, N_("add a Signed-off-by trailer")),
-- 
2.29.0.rc1