Subject: Re: [Bug] Stashing during merge loses MERGING state

From: Tassilo Horn <[email-masked]>
Date: Thu, 11 Mar 2021 21:31:09 +0100

Jeff King <[email-masked]> writes:

Hi Jeff,

>> What did you expect to happen? (Expected behavior)
>> 
>> I expected that stashing during a merge will keep the MERGING state.
>
> Thanks for providing a clear recipe and expectation. However, I think
> Git is working here as intended. The MERGE_HEAD file (which is how "git
> status", the prompt, etc figure out that we're in the middle of a merge)
> is cleaned up when stash runs "git reset --hard" under the hood.
>
> However, I don't think we would want to _not_ clear that file. The
> conflicted merge placed some changes into the index and working tree
> representing what happened on the branch you're merging in. Then
> making the stash (and the reset of the working tree) removes those
> changes. If we were to leave MERGE_HEAD in place and you ran "git
> commit", then it would create a merge commit that claims to have
> incorporated everything from the other branch, but has quietly dropped
> those changes as part of the merge resolution.

Yes, that makes sense.

>> Or that popping the stash again would also restore the MERGING state.
>
> This would make more sense: the stash records that part of the state,
> and then we make it available again later when the stash is applied.
> However, that feature doesn't exist yet.

Too bad.

> I can't offhand think of a reason it couldn't be implemented. It's
> possible that it would mess with somebody else's workflow (e.g., they
> think it's useful to stash some changes independent of the merging
> state, and then apply it later, perhaps while replaying the same or a
> similar merge). So it might need to be tied to a command-line option
> or similar.

Everything breakes someones workflow [1], so an option would be fine.

However, I'd suggest to protect users shooting in their foot with a
warning and confirmation query for the time being.  I consider myself a
quite experienced git user but this stash trouble today came totally
unexpected.  And I've asked on [email-masked] and got no answer
which is totally uncommon.  So I guess that this stash during merge
thing is pretty much a gray area.

Bye,
Tassilo

[1] https://xkcd.com/1172/