threads / discuss / 42837

[feature request] Warn about or prevent --amend commits that don't change anything

Subject: [feature request] Warn about or prevent --amend commits that don't change anything

## tl;dr

3 messages between Jul 13, 2016 and Jul 13, 2016.

replies: 2people: 2as markdown or json

Bergi· Jul 13, 2016, 18:56 UTC · lore

Hello,

when nothing is staged in the index then `git commit` warns about this fact with either "nothing to commit, working directory clean" or "no changes added to commit". However, `git commit --amend --no-edit` will happily record a new commit that differs in nothing than its commit date from the original.

This is unexpected and can lead to mistakes. Without running `git status`, the user will not notice that his unstaged changes were not commited, as everything behaves as expected otherwise (the success output from `commit`, the new commit id in the log, `push` requiring the force option, etc).

I understand that `--amend` is (can be) used for editing commit messages, authors, authoring dates etc. I would however like to see any `--amend` command that results in no changes to the tree, the commit message and the authoring metadata reject the commit with an appropriate warning similar to the one that a plain `git commit` would present. It should be overrideable by the `--allow-emtpy` parameter as well.

If this change detection is somehow unfeasible, I would at least like the `git commit --amend --no-edit` command (with no other flags) to check the tree in the same way as `git commit` does, as the intention of `--no-edit` is even more clear and running the command is more obviously a mistake/lapse.

Kind regards,
  Bergi

Junio C Hamano· Jul 13, 2016, 19:16 UTC · re: Bergi · lore

Re: [feature request] Warn about or prevent --amend commits that don't change anything

Bergi <a.d.bergi@web.de> writes:

Show 7 quoted lines

> when nothing is staged in the index then `git commit` warns about this
> fact with either "nothing to commit, working directory clean" or "no
> changes added to commit".
> However, `git commit --amend --no-edit` will happily record a new
> commit that differs in nothing than its commit date from the original.
>
> This is unexpected and can lead to mistakes.

What kind of "mistake" are you afraid of?

I can sort of see that "git commit --amend" might want to see two summary diffstat output at the end, unlike "git commit" that shows what changes were recorded relative to the parent. In addition to that "final result is different in this way from the parent" output, you might also want "this is the change you made by amending" and knowing the fact that you can notice you didn't add anything by the latter being empty _might_ give you an additional peace of mind.

But is that the kind of mistake you are worried about? IOW, you thought you made and added changes X, Y and Z to the index before running your "commit --amend", but you forgot the "add" step and did not add anything? If so, even the second diff i.e. "this is what you changed by amending" would not help very much, and your "you need --allow-empty if you really do not want any changes to the tree" would not either, if you added X and Y but forgot to add Z.

So I am sensing a slight XY problem here.

Bergi· Jul 13, 2016, 21:02 UTC · re: Junio C Hamano · lore

Re: [feature request] Warn about or prevent --amend commits that don't change anything

Junio C Hamano schrieb:

Show 9 quoted lines

> Bergi <a.d.bergi@web.de> writes:
>
>> when nothing is staged in the index then `git commit` warns about this
>> fact with either "nothing to commit, working directory clean" or "no
>> changes added to commit".
>> However, `git commit --amend --no-edit` will happily record a new
>> commit that differs in nothing than its commit date from the original.
>
> What kind of "mistake" are you afraid of?

The particular mistake that happened to me was that I `git push -f origin`'ed the newly created commit (which worked as expected, overwriting the original commit) and then leaving my PC in the belief that I had successfully pushed my changes.

Show 7 quoted lines

> I can sort of see that "git commit --amend" might want to see two
> summary diffstat output at the end, unlike "git commit" that shows
> what changes were recorded relative to the parent.  In addition to
> that "final result is different in this way from the parent" output,
> you might also want "this is the change you made by amending" and
> knowing the fact that you can notice you didn't add anything by the
> latter being empty _might_ give you an additional peace of mind.

Yes, that would be incredibly helpful as well, but is not what I am after here.

However `git commit --amend` already shows me that I still have "changes not staged for commit" when editing the commit message, so that would've been enough for my use case. The problem is that I used `git commit --amend --no-edit`, which did neither warn me about missing staged changes nor existing unstaged changes. If nothing is staged and the user does not intend to edit any metadata, git should be able to deduce that the user (me) did forget something.

> But is that the kind of mistake you are worried about?  IOW, you
> thought you made and added changes X, Y and Z to the index before
> running your "commit --amend", but you forgot the "add" step and did
> not add anything?

Yes, exactly.

> If so, […] your "you need --allow-empty if you really do not want
> any changes to the tree" would not [help much] either, if you added
> X and Y but forgot to add Z.

A good remark. Maybe in that case it could warn about unstaged edits in the case of --no-edit but still succeed.

> So I am sensing a slight XY problem here.

That might well be, I'm just here to tell my story, it's the designers that need to decide at which step I went wrong and which parts could be improved.

Kind regards,
  Bergi