# "Losing" MERGE_HEAD 2 messages from 2019-05-31 to 2019-05-31. Participants: Bryan Turner, Elijah Newren. Thread: https://gitlist.dev/t/51204 ## Bryan Turner, 2019-05-31 04:16 Subject: "Losing" MERGE_HEAD Message-ID: URL: https://gitlist.dev/e/CAGyf7-EgiWtt0xu9nfYdhafZ6D70nSxbNYAguFrN8OWRqWmzGQ%40mail.gmail.com ``` I was looking through the commit history in a repository I work in and I found a place where someone had created a merge, but somewhere between "git merge" and "git commit" the fact that it was a merge was "lost". Instead they ended up with a really big commit that applied all the changes from the merged-in branch. A really easy way to reproduce this is: git merge master #Assume this has conflicts, or use --no-commit git checkout -b some-new-branch When the checkout runs, MERGE_HEAD et al are deleted without any sort of warning, but the uncommitted changes are not lost. If a user then runs "git commit", and doesn't notice that there's no helpful "It looks like you may be committing a merge", they'll create a new, non-merge commit that essentially reapplies all the changes they merged in. I'm pretty familiar with Git and I make this mistake at least a few times a year. So far I've always caught it during the commit, though. Unfortunately, in this case, the bad "merge" wasn't noticed before it made its way to master, so now it's there for good. I'm not sure what there is to do about this. It's clear it's a long-standing behavior. One approach might be to introduce a warning when changing branches deletes MERGE_*. A different one might be to fail to change branches without something like --force. I'm not sure either is _better_ than the current behavior, but they're certainly _clearer_. That said, perhaps this behavior is something someone relies on. Best regards, Bryan Turner ``` ## Elijah Newren, 2019-05-31 06:03 Subject: Re: "Losing" MERGE_HEAD Message-ID: URL: https://gitlist.dev/e/CABPp-BHramOjqpH0Rz-PEKbi0TX_sKOYvLiZ2Pb%3DhEpViaShmw%40mail.gmail.com In-Reply-To: ``` On Thu, May 30, 2019 at 9:19 PM Bryan Turner wrote: > > I was looking through the commit history in a repository I work in and > I found a place where someone had created a merge, but somewhere > between "git merge" and "git commit" the fact that it was a merge was > "lost". Instead they ended up with a really big commit that applied > all the changes from the merged-in branch. > > A really easy way to reproduce this is: > git merge master #Assume this has conflicts, or use --no-commit > git checkout -b some-new-branch > > When the checkout runs, MERGE_HEAD et al are deleted without any sort > of warning, but the uncommitted changes are not lost. If a user then > runs "git commit", and doesn't notice that there's no helpful "It > looks like you may be committing a merge", they'll create a new, > non-merge commit that essentially reapplies all the changes they > merged in. > > I'm pretty familiar with Git and I make this mistake at least a few > times a year. So far I've always caught it during the commit, though. > Unfortunately, in this case, the bad "merge" wasn't noticed before it > made its way to master, so now it's there for good. > > I'm not sure what there is to do about this. It's clear it's a > long-standing behavior. One approach might be to introduce a warning > when changing branches deletes MERGE_*. A different one might be to > fail to change branches without something like --force. I'm not sure > either is _better_ than the current behavior, but they're certainly > _clearer_. That said, perhaps this behavior is something someone > relies on. > > Best regards, > Bryan Turner Discussed in detail recently starting at https://public-inbox.org/git/CACsJy8Axa5WsLSjiscjnxVK6jQHkfs-gH959=YtUvQkWriAk5w@mail.gmail.com/ resulting in https://public-inbox.org/git/20190329103919.15642-8-pclouds@gmail.com/ and https://public-inbox.org/git/20190329103919.15642-24-pclouds@gmail.com/ I think we should still do the follow up for checkout, as mentioned at https://public-inbox.org/git/CABPp-BHX1gRhTdurAwrPg60Hk-OuhbrEN=4zatx4OOUo-DkQvw@mail.gmail.com/ It's good to get extra feedback that this isn't just theoretical but is causing people actual problems. Do you want to take the time to make the change I suggested in the last email above and propose it to the list? I think the main thing needed is just a good commit message and getting feedback and thoughts from others; your description above was well written and I'm busy on other things right now, so if you'd like to tackle it, I'd appreciate it. If not, I will hopefully remember to get back to it eventually. Hope that helps, Elijah ```