rebase -i: teach --autosquash to work with amend!

If the commit subject starts with "amend!" then rearrange it like a
"fixup!" commit and replace `pick` command with `fixup -C` command,
which is used to fixup up the content if any and replaces the original
commit message with amend! commit's message.

Original-patch-by: Phillip Wood <[email protected]>
Mentored-by: Christian Couder <[email protected]>
Mentored-by: Phillip Wood <[email protected]>
Signed-off-by: Charvi Mendiratta <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: charvi-077

sequencer.c

@@ -5662,6 +5662,12 @@ static int subject2item_cmp(const void *fndata,
 
 define_commit_slab(commit_todo_item, struct todo_item *);
 
+static inline int skip_fixup_amend_squash(const char *subject, const char **p) {
+	return skip_prefix(subject, "fixup! ", p) ||
+	       skip_prefix(subject, "amend! ", p) ||
+	       skip_prefix(subject, "squash! ", p);
+}
+
 /*
  * Rearrange the todo list that has both "pick commit-id msg" and "pick
  * commit-id fixup!/squash! msg" in it so that the latter is put immediately
@@ -5720,15 +5726,13 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 		format_subject(&buf, subject, " ");
 		subject = subjects[i] = strbuf_detach(&buf, &subject_len);
 		unuse_commit_buffer(item->commit, commit_buffer);
-		if ((skip_prefix(subject, "fixup! ", &p) ||
-		     skip_prefix(subject, "squash! ", &p))) {
+		if (skip_fixup_amend_squash(subject, &p)) {
 			struct commit *commit2;
 
 			for (;;) {
 				while (isspace(*p))
 					p++;
-				if (!skip_prefix(p, "fixup! ", &p) &&
-				    !skip_prefix(p, "squash! ", &p))
+				if (!skip_fixup_amend_squash(p, &p))
 					break;
 			}
 
@@ -5758,9 +5762,14 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 		}
 		if (i2 >= 0) {
 			rearranged = 1;
-			todo_list->items[i].command =
-				starts_with(subject, "fixup!") ?
-				TODO_FIXUP : TODO_SQUASH;
+			if (starts_with(subject, "fixup!")) {
+				todo_list->items[i].command = TODO_FIXUP;
+			} else if (starts_with(subject, "amend!")) {
+				todo_list->items[i].command = TODO_FIXUP;
+				todo_list->items[i].flags = TODO_REPLACE_FIXUP_MSG;
+			} else {
+				todo_list->items[i].command = TODO_SQUASH;
+			}
 			if (tail[i2] < 0) {
 				next[i] = next[i2];
 				next[i2] = i;

t/t3437-rebase-fixup-options.sh

@@ -210,4 +210,16 @@ test_expect_success 'sequence squash, fixup & fixup -c gives combined message' '
 	test_cmp_rev HEAD^ A
 '
 
+test_expect_success 'fixup -C works upon --autosquash with amend!' '
+	git checkout --detach branch &&
+	FAKE_COMMIT_AMEND=squashed \
+		FAKE_MESSAGE_COPY=actual-squash-message \
+		git -c commit.status=false rebase -ik --autosquash \
+						--signoff A &&
+	git diff-tree --exit-code --patch HEAD branch -- &&
+	test_cmp_rev HEAD^ A &&
+	test_i18ncmp "$TEST_DIRECTORY/t3437/expected-squash-message" \
+		actual-squash-message
+'
+
 test_done