Amending a signed commit overwrites author

[ItsHarper]

Describe the bug

Amending a signed commit overwrites the author (bad) and the committer (good).

Amending an unsigned commit does not overwrite the author (good), but it also does not overwrite the committer (bad).

To Reproduce

1. Check out a branch where the latest commit was authored and committed by someone else
2. Run git log --pretty=full -n 1 and verify that the Author field shows someone other than you
3. Stage changes
4. Open the commit dialog
5. Press Ctrl-A to make the pending commit be an amend operation
6. Press Ctrl-D to finish the commit
7. Run git log --pretty=full -n 1 again
8. Observe that either the author or committer is wrong (depending on whether the commit you amended was signed)

Expected behavior

Amending a commit should overwrite the committer, but not the author.

Context

• OS: Chimera Linux (updated as of 2025-11-20)
• GitUI Version: 0.27.0
• Rust version: 1.91.0

[cruessler]

I’ll have a look!

[cruessler]

Currently, this seems to be somewhat intentional as the code for amending a commit passes None for committer which results in the committer being unchanged. I suggest we change that and override the committer with the current user, that is whatever is returned by signature_allow_undefined_name (which usually is git config --get user.name/email). I’ll prepare a PR soon!

gitui/asyncgit/src/sync/commit.rs

Lines 43 to 50 in 37d3dd2

	let new_id = commit.amend(
	Some("HEAD"),
	None,
	None,
	None,
	Some(msg),
	Some(&tree),
	)?;

[extrawurst]

seems to be somewhat intentional [..] results in the committer being unchanged

isnt that exactly the opposite of what the bug report states?

[cruessler]

seems to be somewhat intentional [..] results in the committer being unchanged

isnt that exactly the opposite of what the bug report states?

You’re absolutely right! Then I can’t seem to reproduce as the author is not overwritten if I do an amend using gitui. (This observation made me think we should probably change the committer if we amend, but now I’m not so sure anymore.) I can also try and check on a different machine to see whether I’m missing anything.

[ItsHarper]

This observation made me think we should probably change the committer if we amend, but now I’m not so sure anymore.

My understanding is that the committer should change, yeah

Let me double-check I can reproduce myself.

[extrawurst]

@ItsHarper

My understanding is that the committer should change, yeah

But your bug report says:

Observe that you are now listed as the commit author

So what is it ? 🙈

[ItsHarper]

@ItsHarper

My understanding is that the committer should change, yeah

But your bug report says:

Observe that you are now listed as the commit author

So what is it ? 🙈

"Committer" and "Author" are two different things. The "Author" is supposed to be the original author of the commit. The "Committer" is the last person who modified the commit in some way (amend, rebase, etc).

[ItsHarper]

Screenshot demonstrating the correct behavior

The committer changes, but the author does not

---

(I meant to have that first line be git config set user.name me for clarity; setting log.showSignature is irrelevant)

Screenshot demonstrating the incorrect behavior

These commands were performed immediately after the previous screenshot was taken. When I ran gitui, I amended the commit and did nothing else. The author has erroneously been changed.

[ItsHarper]

In case you're looking at email notifications, I've edited my last comment to have screenshots that demonstrate both the correct git behavior and the incorrect gitui behavior (it does reproduce for me).

[ItsHarper]

the code for amending a commit passes None for committer which results in the committer being unchanged.

When in doubt, read the docs:

This creates a new commit that is exactly the same as the old commit, except that any non-None values will be updated. (emphasis mine)

You have to explicitly provide the original author to amend().

[ItsHarper]

Wait, I think the docs agree with you. Quite frankly, I'm not sure how I was reading it previously...

Is this a bug in my distribution's version of libgit2? Chimera Linux packages 1.9.1, the latest stable release.

[ItsHarper]

OK, I figured out why you couldn't reproduce it. The behavior is different depending on whether you're amending a signed commit.

When amending a signed commit, both author and committer are overwritten.

When amending an unsigned commit, neither author nor committer are overwritten.

Both behaviors are wrong, just in opposite directions. I've edited the issue description.