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[PATCH] commit: refuse to amend during conflict resolution

From
Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date
Aug 26, 2026, 05:21 UTC
Message-ID
<pull.2389.git.git.1787721681893.gitgitgadget@gmail.com>
From: Elijah Newren <newren@gmail.com>
Running `git commit --amend` during conflict resolution is an ugly
foot-gun.  For many years, we have rejected amending during conflict
resolution in the middle of
  - a merge
  - a cherry-pick
However, this was never extended to other operations that can also
produce conflicts:
  - an `am` operation
  - a revert
  - a rebase
Extend it to handle these other cases now.
Extending to `am`, revert, and the apply backend of rebase are fairly
straightforward.  However, with the merge backend of rebase we have to
be more careful, since it powers interactive rebases and
  - the interactive machinery internally uses `git commit --amend` for
    `squash` and `reword` directives
  - users are expected to `git commit --amend` after hitting an `edit`
    or `break` directive
So, we need to be careful with rebase to only reject amending when doing
conflict resolution.

A few files under the rebase-merge/ directory provide us the necessary information:

  - stopped-sha is written only when the rebase stops and hands control
    back to the user, so its presence marks a genuine stop -- as opposed
    to the sequencer's own internal `git commit --amend` while applying
    a squash, fixup, or reword, during which no stopped-sha exists.
  - amend is written only when the rebase stops with HEAD already
    pointing at the commit the user is meant to amend: a clean `edit`,
    or a fast-forward `reword`.  Its absence at a stop therefore means
    the commit did not apply, so HEAD is the previously-applied commit
    rather than the one being rebased -- exactly the case we refuse.

So for the merge backend we die when stopped-sha exists and amend does not. This covers a plain conflicted pick as well as a conflicted `edit` (both leave HEAD on the previously-applied commit), while still allowing a clean `edit` or `reword` stop and a `break` stop (no stopped-sha). stopped-sha is unlinked at the start of the resume loop, so a resumed squash's internal amend is unaffected.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
    commit: refuse to amend during conflict resolution
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2389%2Fnewren%2Frefuse-amend-during-conflicts-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2389/newren/refuse-amend-during-conflicts-v1
Pull-Request: https://github.com/git/git/pull/2389
 builtin/commit.c                | 41 ++++++++++++++++
 t/t3404-rebase-interactive.sh   | 87 +++++++++++++++++++++++++++++++++
 t/t3507-cherry-pick-conflict.sh | 11 +++++
 t/t4151-am-abort.sh             | 11 +++++
 4 files changed, 150 insertions(+)
diff --git a/builtin/commit.c b/builtin/commit.c
index 28f6174503..a9fd04366e 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -30,6 +30,7 @@
 #include "path.h"
 #include "preload-index.h"
 #include "read-cache.h"
+#include "refs.h"
 #include "repository.h"
 #include "string-list.h"
 #include "rerere.h"
@@ -1336,6 +1337,46 @@ static int parse_and_validate_options(int argc, const char *argv[],
 		else if (whence == FROM_REBASE_PICK)
 			die(_("You are in the middle of a rebase -- cannot amend."));
 	}
+	if (amend && whence == FROM_COMMIT) {
+		char *applying, *apply_dir, *stopped_sha, *amend_marker;
+		int in_am, conflicted_stop;
+
+		/* Check middle of revert */
+		if (refs_ref_exists(get_main_ref_store(the_repository),
+				    "REVERT_HEAD"))
+			die(_("You are in the middle of a revert -- cannot amend."));
+
+		/* Check middle of `am` */
+		applying = repo_git_path(the_repository,
+					 "rebase-apply/applying");
+		in_am = file_exists(applying);
+
+		free(applying);
+		if (in_am)
+			die(_("You are in the middle of an am session -- cannot amend."));
+
+		/* Check middle of rebase specifically stopped for conflicts */
+		apply_dir = repo_git_path(the_repository,
+					  "rebase-apply");
+		stopped_sha = repo_git_path(the_repository,
+					    "rebase-merge/stopped-sha");
+		amend_marker = repo_git_path(the_repository,
+					     "rebase-merge/amend");
+		/*
+		 * The apply backend only ever stops for conflicts; the
+		 * merge backend writes stopped-sha but omits `amend`,
+		 * which it writes only at a clean edit/reword stop.
+		 */
+		conflicted_stop =
+			file_exists(apply_dir) ||
+			(file_exists(stopped_sha) && !file_exists(amend_marker));
+
+		free(apply_dir);
+		free(stopped_sha);
+		free(amend_marker);
+		if (conflicted_stop)
+			die(_("You are resolving conflicts during a rebase -- cannot amend."));
+	}
 	if (fixup_message && squash_message)
 		die(_("options '%s' and '%s' cannot be used together"), "--squash", "--fixup");
 	die_for_incompatible_opt4(!!use_message, "-C",
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index ff11abb2f2..01d4735b3b 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -1884,6 +1884,93 @@ test_expect_success 'correct error message for commit --amend after empty pick'
 	test_grep "middle of a rebase -- cannot amend." err
 '
 
+test_expect_success 'commit --amend is refused at a rebase conflict stop' '
+	test_when_finished "git rebase --abort" &&
+	git checkout --detach conflict-branch &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 3" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i A
+	) &&
+	test_path_is_file .git/rebase-merge/patch &&
+	test_path_is_missing .git/rebase-merge/amend &&
+	echo resolved >conflict &&
+	git add conflict &&
+	test_must_fail git commit --amend --no-edit 2>err &&
+	test_grep "You are resolving conflicts during a rebase -- cannot amend" err
+'
+
+test_expect_success 'commit --amend is refused when an "edit" pick conflicts' '
+	test_when_finished "git rebase --abort" &&
+	git checkout --detach conflict-branch &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 edit 3" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i A
+	) &&
+	test_path_is_file .git/rebase-merge/patch &&
+	test_path_is_missing .git/rebase-merge/amend &&
+	echo resolved >conflict &&
+	git add conflict &&
+	test_must_fail git commit --amend --no-edit 2>err &&
+	test_grep "You are resolving conflicts during a rebase -- cannot amend" err
+'
+
+test_expect_success 'commit --amend is allowed at a rebase edit stop' '
+	test_when_finished "git rebase --abort" &&
+	git checkout --detach no-conflict-branch &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1 2 3 4" &&
+		export FAKE_LINES &&
+		git rebase -i A
+	) &&
+	test_path_is_file .git/rebase-merge/amend &&
+	echo tweak >fileJ &&
+	git add fileJ &&
+	git commit --amend --no-edit
+'
+
+test_expect_success 'commit --amend is allowed at a rebase break stop' '
+	test_when_finished "git rebase --abort" &&
+	git checkout --detach no-conflict-branch &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="break 1 2 3 4" &&
+		export FAKE_LINES &&
+		git rebase -i A
+	) &&
+	test_must_fail git rev-parse --verify REBASE_HEAD &&
+	echo tweak >fileJ &&
+	git add fileJ &&
+	git commit --amend --no-edit
+'
+
+test_expect_success 'commit --amend is refused at an apply-backend conflict stop' '
+	test_when_finished "rm -rf apply-backend" &&
+	test_create_repo apply-backend &&
+	(
+		cd apply-backend &&
+		test_commit base file &&
+		git branch -M mainline &&
+		test_commit upstream file upstream &&
+		git checkout -b side mainline~1 &&
+		test_commit conflicting file side &&
+		test_commit unrelated other &&
+		test_must_fail git rebase --apply mainline &&
+		# the apply backend only ever stops for conflicts, and
+		# leaves HEAD on the previously-applied commit
+		test_path_is_dir .git/rebase-apply &&
+		test_path_is_missing .git/rebase-apply/applying &&
+		echo resolved >file &&
+		git add file &&
+		test_must_fail git commit --amend --no-edit 2>err &&
+		test_grep "You are resolving conflicts during a rebase -- cannot amend" err
+	)
+'
+
 test_expect_success 'todo has correct onto hash' '
 	GIT_SEQUENCE_EDITOR=cat git rebase -i no-conflict-branch~4 no-conflict-branch >actual &&
 	onto=$(git rev-parse --short HEAD~4) &&
diff --git a/t/t3507-cherry-pick-conflict.sh b/t/t3507-cherry-pick-conflict.sh
index 44596cb1e8..42de398f76 100755
--- a/t/t3507-cherry-pick-conflict.sh
+++ b/t/t3507-cherry-pick-conflict.sh
@@ -364,6 +364,17 @@ test_expect_success 'failed revert sets REVERT_HEAD' '
 	test_cmp_rev picked REVERT_HEAD
 '
 
+test_expect_success 'commit --amend of revert fails' '
+	pristine_detach initial &&
+
+	test_must_fail git revert picked &&
+	echo resolved >foo &&
+	git add foo &&
+	test_must_fail git commit --amend 2>err &&
+
+	test_grep "in the middle of a revert -- cannot amend." err
+'
+
 test_expect_success 'successful revert does not set REVERT_HEAD' '
 	pristine_detach base &&
 	git revert base &&
diff --git a/t/t4151-am-abort.sh b/t/t4151-am-abort.sh
index 8e1ecf8a68..9313a074b2 100755
--- a/t/t4151-am-abort.sh
+++ b/t/t4151-am-abort.sh
@@ -63,6 +63,17 @@ do
 
 done
 
+test_expect_success 'commit --amend during a failed am fails' '
+	git reset --hard initial &&
+	cp file-2-expect file-2 &&
+	test_must_fail git am 000[1245]-*.patch &&
+	echo resolved >file-1 &&
+	git add file-1 &&
+	test_must_fail git commit --amend 2>err &&
+	test_grep "in the middle of an am session -- cannot amend." err &&
+	git am --abort
+'
+
 test_expect_success 'am -3 --skip removes otherfile-4' '
 	git reset --hard initial &&
 	test_must_fail git am -3 0003-*.patch &&

base-commit: 2c3adbb2c475981e340c79fdc5e7f4f9b5d9054e

-- 
gitgitgadget
Next: Phillip Wood
Message 1 of 43 in “commit: refuse to amend during conflict resolution”
  1. commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Aug 26, 2026
  2. Phillip WoodAug 26, 2026
  3. Elijah NewrenAug 27, 2026
  4. Junio C HamanoAug 26, 2026
  5. Elijah NewrenAug 27, 2026
  6. Junio C HamanoAug 26, 2026
  7. Elijah NewrenAug 27, 2026
  8. 0/3 commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Aug 27, 2026
  9. 1/3 commit: reword the empty-commit rebase errorsElijah Newren via GitGitGadget, Aug 27, 2026
  10. Phillip WoodAug 27, 2026
  11. Junio C HamanoAug 27, 2026
  12. Elijah NewrenAug 28, 2026
  13. Junio C HamanoAug 27, 2026
  14. Junio C HamanoAug 27, 2026
  15. Elijah NewrenAug 28, 2026
  16. 2/3 commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Aug 27, 2026
  17. Phillip WoodAug 27, 2026
  18. 3/3 commit: refuse partial commits during conflict resolutionElijah Newren via GitGitGadget, Aug 27, 2026
  19. Phillip WoodAug 27, 2026
  20. Phillip WoodAug 27, 2026
  21. Elijah NewrenAug 27, 2026
  22. 0/5 commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Aug 28, 2026
  23. 1/5 commit: clarify FROM_REBASE_PICK and is_from_rebase() namesElijah Newren via GitGitGadget, Aug 28, 2026
  24. Junio C HamanoAug 28, 2026
  25. Elijah NewrenAug 28, 2026
  26. 2/5 commit: allow a partial commit when a rebase pick becomes emptyElijah Newren via GitGitGadget, Aug 28, 2026
  27. Junio C HamanoAug 28, 2026
  28. 3/5 commit: reword the empty-commit rebase amend errorElijah Newren via GitGitGadget, Aug 28, 2026
  29. Junio C HamanoAug 28, 2026
  30. 4/5 commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Aug 28, 2026
  31. 5/5 commit: refuse partial commits during conflict resolutionElijah Newren via GitGitGadget, Aug 28, 2026
  32. Junio C HamanoAug 28, 2026
  33. 0/5 commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Sep 1, 2026
  34. 1/5 commit: clarify FROM_REBASE_PICK and is_from_rebase() namesElijah Newren via GitGitGadget, Sep 1, 2026
  35. Phillip WoodSep 2, 2026
  36. 2/5 commit: allow a partial commit when a rebase pick becomes emptyElijah Newren via GitGitGadget, Sep 1, 2026
  37. Phillip WoodSep 2, 2026
  38. 3/5 commit: reword the empty-commit rebase amend errorElijah Newren via GitGitGadget, Sep 1, 2026
  39. Phillip WoodSep 2, 2026
  40. 4/5 commit: refuse to amend during conflict resolutionElijah Newren via GitGitGadget, Sep 1, 2026
  41. Phillip WoodSep 2, 2026
  42. 5/5 commit: refuse partial commits during conflict resolutionElijah Newren via GitGitGadget, Sep 1, 2026
  43. Phillip WoodSep 2, 2026

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