# [BUG?] git checkout -b removes MERGE_HEAD 4 messages from 2010-11-18 to 2010-11-18. Participants: Jan Hudec, Junio C Hamano, Jeff King. Thread: https://gitlist.dev/t/25778 ## Jan Hudec, 2010-11-18 07:15 Subject: [BUG?] git checkout -b removes MERGE_HEAD Message-ID: <456aec650e66bba518b8a5ec88c88a6b.squirrel@artax.karlin.mff.cuni.cz> URL: https://gitlist.dev/e/456aec650e66bba518b8a5ec88c88a6b.squirrel%40artax.karlin.mff.cuni.cz ``` Hello all, I am not sure whether it is a bug or not, but it definitely did surprise me a lot. The use-case was as follows: - I checked out master and ran a merge from branch (let's call it "branch"). It had a lot of conflicts, so I needed to test the result well. - During the testing I found a problem, but it may have already existed on master before the merge. - Therefore I needed to return to clean master, test it and return to the merge. So I thought I'd commit the merge to a temporary branch, test master again and merge the temporary to master if the problem is not from the merge. So I did: $ git checkout -b temp $ git commit OOPS! It forgot it was a merge. Yes, I could have simply commited to master and reset --hard it back. But I didn't expect it to forget it was a merge in the first place. After all, it does NOT touch the index nor the working tree, so why should it clear the MERGE_HEAD and MERGE_MSG? So should this behaviour be changed? Thanks, Jan -- - Jan Hudec ``` ## Junio C Hamano, 2010-11-18 18:39 Subject: Re: [BUG?] git checkout -b removes MERGE_HEAD Message-ID: <7vwroabhng.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7vwroabhng.fsf%40alter.siamese.dyndns.org In-Reply-To: <456aec650e66bba518b8a5ec88c88a6b.squirrel@artax.karlin.mff.cuni.cz> ``` "Jan Hudec" writes: > - During the testing I found a problem, but it may have already > existed on master before the merge. > - Therefore I needed to return to clean master, test it and return > to the merge. So I thought I'd commit the merge to a temporary > branch, test master again and merge the temporary to master if > the problem is not from the merge. So I did: > > $ git checkout -b temp > $ git commit > > OOPS! It forgot it was a merge. I think it was an oversight by the author of 91dcdfd (Make "git checkout" create new branches on demand, 2005-07-11) who forgot that he also did ef0bfa2 (Remove MERGE_HEAD in "git checkout/reset", 2005-06-21). The rationale for the removal of MERGE_HEAD from the earlier commit is: [this command] will end up resetting the index to some specific head, and any unresolved merge will be forgotten [hence there is no point recording the result as a merge]. but when used with -b no such "resetting of the index" happens. Having said that, changing it not to remove MERGE_HEAD and MERGE_MSG is probably not sufficient, as MERGE_MSG would likely to already record to which branch you are recording the merge (I didn't check, though). ``` ## Jan Hudec, 2010-11-18 19:01 Subject: Re: [BUG?] git checkout -b removes MERGE_HEAD Message-ID: <20101118190101.GP3693@efreet.light.src> URL: https://gitlist.dev/e/20101118190101.GP3693%40efreet.light.src In-Reply-To: <7vwroabhng.fsf@alter.siamese.dyndns.org> ``` On Thu, Nov 18, 2010 at 10:39:31 -0800, Junio C Hamano wrote: > "Jan Hudec" writes: > > > So I did: > > > > $ git checkout -b temp > > $ git commit > > > > OOPS! It forgot it was a merge. > > I think it was an oversight by the author of 91dcdfd (Make "git checkout" > create new branches on demand, 2005-07-11) who forgot that he also did > ef0bfa2 (Remove MERGE_HEAD in "git checkout/reset", 2005-06-21). The > rationale for the removal of MERGE_HEAD from the earlier commit is: > > [this command] will end up resetting the index to some specific > head, and any unresolved merge will be forgotten [hence there is no > point recording the result as a merge]. > > but when used with -b no such "resetting of the index" happens. > > Having said that, changing it not to remove MERGE_HEAD and MERGE_MSG is > probably not sufficient, as MERGE_MSG would likely to already record to > which branch you are recording the merge (I didn't check, though). I believe it indeed does. However since it's now just a template for the commit message, it can be fixed up by the user. If he actually wants to, that is. In my case, I only needed to stash the changes, so I could switch back to 'master' (left merge parent) to test the bug I was seeing was already there and than I merged the temporary branch to 'master' (which was fast forward). So the message saying I merged to 'master' was actually appropriate even when I was commiting to some other ref. -- Jan 'Bulb' Hudec ``` ## Jeff King, 2010-11-18 19:26 Subject: Re: [BUG?] git checkout -b removes MERGE_HEAD Message-ID: <20101118192647.GD30438@sigill.intra.peff.net> URL: https://gitlist.dev/e/20101118192647.GD30438%40sigill.intra.peff.net In-Reply-To: <7vwroabhng.fsf@alter.siamese.dyndns.org> ``` On Thu, Nov 18, 2010 at 10:39:31AM -0800, Junio C Hamano wrote: > I think it was an oversight by the author of 91dcdfd (Make "git checkout" > create new branches on demand, 2005-07-11) who forgot that he also did > ef0bfa2 (Remove MERGE_HEAD in "git checkout/reset", 2005-06-21). The > rationale for the removal of MERGE_HEAD from the earlier commit is: > > [this command] will end up resetting the index to some specific > head, and any unresolved merge will be forgotten [hence there is no > point recording the result as a merge]. > > but when used with -b no such "resetting of the index" happens. It is not necessarily about "-b" is it? It is about moving to a different commit. So I would think that on branch "master": # should clear MERGE_HEAD git checkout foo # should not clear MERGE_HEAD; it's a no-op, and we have in the past # encouraged people to run this to see the ahead/behind count git checkout # or git checkout master # should clear MERGE_HEAD; we are moving to a new commit git checkout -b foo some_commit # should not clear MERGE_HEAD; this is Jan's case git checkout -b foo # or git checkout -b foo master -Peff ```