Merge branch 'pw/rebase-r-fixes' into maint

Various bugs in "git rebase -r" have been fixed.

* pw/rebase-r-fixes:
  rebase -r: fix merge -c with a merge strategy
  rebase -r: don't write .git/MERGE_MSG when fast-forwarding
  rebase -i: add another reword test
  rebase -r: make 'merge -c' behave like reword

sequencer.c

@@ -983,7 +983,8 @@ static int run_git_commit(const char *defmsg,
 
 	cmd.git_cmd = 1;
 
-	if (is_rebase_i(opts) && read_env_script(&cmd.env_array)) {
+	if (is_rebase_i(opts) && !(!defmsg && (flags & AMEND_MSG)) &&
+	    read_env_script(&cmd.env_array)) {
 		const char *gpg_opt = gpg_sign_opt_quoted(opts);
 
 		return error(_(staged_changes_advice),
@@ -3739,10 +3740,9 @@ static struct commit *lookup_label(const char *label, int len,
 static int do_merge(struct repository *r,
 		    struct commit *commit,
 		    const char *arg, int arg_len,
-		    int flags, struct replay_opts *opts)
+		    int flags, int *check_todo, struct replay_opts *opts)
 {
-	int run_commit_flags = (flags & TODO_EDIT_MERGE_MSG) ?
-		EDIT_MSG | VERIFY_MSG : 0;
+	int run_commit_flags = 0;
 	struct strbuf ref_name = STRBUF_INIT;
 	struct commit *head_commit, *merge_commit, *i;
 	struct commit_list *bases, *j, *reversed = NULL;
@@ -3816,6 +3816,45 @@ static int do_merge(struct repository *r,
 		goto leave_merge;
 	}
 
+	/*
+	 * If HEAD is not identical to the first parent of the original merge
+	 * commit, we cannot fast-forward.
+	 */
+	can_fast_forward = opts->allow_ff && commit && commit->parents &&
+		oideq(&commit->parents->item->object.oid,
+		      &head_commit->object.oid);
+
+	/*
+	 * If any merge head is different from the original one, we cannot
+	 * fast-forward.
+	 */
+	if (can_fast_forward) {
+		struct commit_list *p = commit->parents->next;
+
+		for (j = to_merge; j && p; j = j->next, p = p->next)
+			if (!oideq(&j->item->object.oid,
+				   &p->item->object.oid)) {
+				can_fast_forward = 0;
+				break;
+			}
+		/*
+		 * If the number of merge heads differs from the original merge
+		 * commit, we cannot fast-forward.
+		 */
+		if (j || p)
+			can_fast_forward = 0;
+	}
+
+	if (can_fast_forward) {
+		rollback_lock_file(&lock);
+		ret = fast_forward_to(r, &commit->object.oid,
+				      &head_commit->object.oid, 0, opts);
+		if (flags & TODO_EDIT_MERGE_MSG)
+			goto fast_forward_edit;
+
+		goto leave_merge;
+	}
+
 	if (commit) {
 		const char *encoding = get_commit_output_encoding();
 		const char *message = logmsg_reencode(commit, NULL, encoding);
@@ -3865,46 +3904,6 @@ static int do_merge(struct repository *r,
 		}
 	}
 
-	/*
-	 * If HEAD is not identical to the first parent of the original merge
-	 * commit, we cannot fast-forward.
-	 */
-	can_fast_forward = opts->allow_ff && commit && commit->parents &&
-		oideq(&commit->parents->item->object.oid,
-		      &head_commit->object.oid);
-
-	/*
-	 * If any merge head is different from the original one, we cannot
-	 * fast-forward.
-	 */
-	if (can_fast_forward) {
-		struct commit_list *p = commit->parents->next;
-
-		for (j = to_merge; j && p; j = j->next, p = p->next)
-			if (!oideq(&j->item->object.oid,
-				   &p->item->object.oid)) {
-				can_fast_forward = 0;
-				break;
-			}
-		/*
-		 * If the number of merge heads differs from the original merge
-		 * commit, we cannot fast-forward.
-		 */
-		if (j || p)
-			can_fast_forward = 0;
-	}
-
-	if (can_fast_forward) {
-		rollback_lock_file(&lock);
-		ret = fast_forward_to(r, &commit->object.oid,
-				      &head_commit->object.oid, 0, opts);
-		if (flags & TODO_EDIT_MERGE_MSG) {
-			run_commit_flags |= AMEND_MSG;
-			goto fast_forward_edit;
-		}
-		goto leave_merge;
-	}
-
 	if (strategy || to_merge->next) {
 		/* Octopus merge */
 		struct child_process cmd = CHILD_PROCESS_INIT;
@@ -3935,7 +3934,10 @@ static int do_merge(struct repository *r,
 				strvec_pushf(&cmd.args,
 					     "-X%s", opts->xopts[k]);
 		}
-		strvec_push(&cmd.args, "--no-edit");
+		if (!(flags & TODO_EDIT_MERGE_MSG))
+			strvec_push(&cmd.args, "--no-edit");
+		else
+			strvec_push(&cmd.args, "--edit");
 		strvec_push(&cmd.args, "--no-ff");
 		strvec_push(&cmd.args, "--no-log");
 		strvec_push(&cmd.args, "--no-stat");
@@ -4035,10 +4037,17 @@ static int do_merge(struct repository *r,
 		 * value (a negative one would indicate that the `merge`
 		 * command needs to be rescheduled).
 		 */
-	fast_forward_edit:
 		ret = !!run_git_commit(git_path_merge_msg(r), opts,
 				       run_commit_flags);
 
+	if (!ret && flags & TODO_EDIT_MERGE_MSG) {
+	fast_forward_edit:
+		*check_todo = 1;
+		run_commit_flags |= AMEND_MSG | EDIT_MSG | VERIFY_MSG;
+		ret = !!run_git_commit(NULL, opts, run_commit_flags);
+	}
+
+
 leave_merge:
 	strbuf_release(&ref_name);
 	rollback_lock_file(&lock);
@@ -4405,9 +4414,8 @@ static int pick_commits(struct repository *r,
 			if ((res = do_reset(r, arg, item->arg_len, opts)))
 				reschedule = 1;
 		} else if (item->command == TODO_MERGE) {
-			if ((res = do_merge(r, item->commit,
-					    arg, item->arg_len,
-					    item->flags, opts)) < 0)
+			if ((res = do_merge(r, item->commit, arg, item->arg_len,
+					    item->flags, &check_todo, opts)) < 0)
 				reschedule = 1;
 			else if (item->commit)
 				record_in_rewritten(&item->commit->object.oid,

t/lib-rebase.sh

@@ -151,3 +151,59 @@ test_editor_unchanged () {
 	EOF
 	test_cmp expect actual
 }
+
+# Set up an editor for testing reword commands
+# Checks that there are no uncommitted changes when rewording and that the
+# todo-list is reread after each
+set_reword_editor () {
+	>reword-actual &&
+	>reword-oid &&
+
+	# Check rewording keeps the original authorship
+	GIT_AUTHOR_NAME="Reword Author"
+	GIT_AUTHOR_EMAIL="reword.author@example.com"
+	GIT_AUTHOR_DATE=@123456
+
+	write_script reword-sequence-editor.sh <<-\EOF &&
+	todo="$(cat "$1")" &&
+	echo "exec git log -1 --pretty=format:'%an <%ae> %at%n%B%n' \
+		>>reword-actual" >"$1" &&
+	printf "%s\n" "$todo" >>"$1"
+	EOF
+
+	write_script reword-editor.sh <<-EOF &&
+	# Save the oid of the first reworded commit so we can check rebase
+	# fast-forwards to it. Also check that we do not write .git/MERGE_MSG
+	# when fast-forwarding
+	if ! test -s reword-oid
+	then
+		git rev-parse HEAD >reword-oid &&
+		if test -f .git/MERGE_MSG
+		then
+			echo 1>&2 "error: .git/MERGE_MSG exists"
+			exit 1
+		fi
+	fi &&
+	# There should be no uncommited changes
+	git diff --exit-code HEAD &&
+	# The todo-list should be re-read after a reword
+	GIT_SEQUENCE_EDITOR="\"$PWD/reword-sequence-editor.sh\"" \
+		git rebase --edit-todo &&
+	echo edited >>"\$1"
+	EOF
+
+	test_set_editor "$PWD/reword-editor.sh"
+}
+
+# Check the results of a rebase after calling set_reword_editor
+# Pass the commits that were reworded in the order that they were picked
+# Expects the first pick to be a fast-forward
+check_reworded_commits () {
+	test_cmp_rev "$(cat reword-oid)" "$1^{commit}" &&
+	git log --format="%an <%ae> %at%n%B%nedited%n" --no-walk=unsorted "$@" \
+		>reword-expected &&
+	test_cmp reword-expected reword-actual &&
+	git log --format="%an <%ae> %at%n%B" -n $# --first-parent --reverse \
+		>reword-log &&
+	test_cmp reword-expected reword-log
+}

t/t3404-rebase-interactive.sh

@@ -839,6 +839,19 @@ test_expect_success 'reword' '
 	git show HEAD~2 | grep "C changed"
 '
 
+test_expect_success 'no uncommited changes when rewording the todo list is reloaded' '
+	git checkout E &&
+	test_when_finished "git checkout @{-1}" &&
+	(
+		set_fake_editor &&
+		GIT_SEQUENCE_EDITOR="\"$PWD/fake-editor.sh\"" &&
+		export GIT_SEQUENCE_EDITOR &&
+		set_reword_editor &&
+		FAKE_LINES="reword 1 reword 2" git rebase -i C
+	) &&
+	check_reworded_commits D E
+'
+
 test_expect_success 'rebase -i can copy notes' '
 	git config notes.rewrite.rebase true &&
 	git config notes.rewriteRef "refs/notes/*" &&

t/t3430-rebase-merges.sh

@@ -172,19 +172,39 @@ test_expect_success 'failed `merge <branch>` does not crash' '
 	grep "^Merge branch ${SQ}G${SQ}$" .git/rebase-merge/message
 '
 
-test_expect_success 'fast-forward merge -c still rewords' '
-	git checkout -b fast-forward-merge-c H &&
+test_expect_success 'merge -c commits before rewording and reloads todo-list' '
+	cat >script-from-scratch <<-\EOF &&
+	merge -c E B
+	merge -c H G
+	EOF
+
+	git checkout -b merge-c H &&
 	(
-		set_fake_editor &&
-		FAKE_COMMIT_MESSAGE=edited \
-			GIT_SEQUENCE_EDITOR="echo merge -c H G >" \
-			git rebase -ir @^
+		set_reword_editor &&
+		GIT_SEQUENCE_EDITOR="\"$PWD/replace-editor.sh\"" \
+			git rebase -i -r D
 	) &&
-	echo edited >expected &&
-	git log --pretty=format:%B -1 >actual &&
-	test_cmp expected actual
+	check_reworded_commits E H
 '
 
+test_expect_success 'merge -c rewords when a strategy is given' '
+	git checkout -b merge-c-with-strategy H &&
+	write_script git-merge-override <<-\EOF &&
+	echo overridden$1 >G.t
+	git add G.t
+	EOF
+
+	PATH="$PWD:$PATH" \
+	GIT_SEQUENCE_EDITOR="echo merge -c H G >" \
+	GIT_EDITOR="echo edited >>" \
+		git rebase --no-ff -ir -s override -Xxopt E &&
+	test_write_lines overridden--xopt >expect &&
+	test_cmp expect G.t &&
+	test_write_lines H "" edited "" >expect &&
+	git log --format=%B -1 >actual &&
+	test_cmp expect actual
+
+'
 test_expect_success 'with a branch tip that was cherry-picked already' '
 	git checkout -b already-upstream main &&
 	base="$(git rev-parse --verify HEAD)" &&