# Has anyone written a hook to block fast forward merges to a branch? 6 messages from 2012-03-21 to 2012-03-21. Participants: Chris Patti, Jeff King, Neal Kreitzinger. Thread: https://gitlist.dev/t/30017 ## Chris Patti, 2012-03-21 18:22 Subject: Has anyone written a hook to block fast forward merges to a branch? Message-ID: URL: https://gitlist.dev/e/CAJ8P3RCQjh1ehjsihAmu8roC1aeRo%3DR0sN2Wm0Y4bVk%3Dst4ivw%40mail.gmail.com ``` I know there are hooks out there to block various other kinds of change, but I was wondering if anyone had specifically ever written one to block fast forward merges. Thanks, -Chris -- Christopher Patti - Geek At Large | GTalk: cpatti@gmail.com | AIM: chrisfeohpatti | P: (260) 54PATTI "Technology challenges art, art inspires technology." - John Lasseter, Pixar ``` ## Jeff King, 2012-03-21 18:40 Subject: Re: Has anyone written a hook to block fast forward merges to a branch? Message-ID: <20120321184051.GB14638@sigill.intra.peff.net> URL: https://gitlist.dev/e/20120321184051.GB14638%40sigill.intra.peff.net In-Reply-To: ``` On Wed, Mar 21, 2012 at 02:22:46PM -0400, Chris Patti wrote: > I know there are hooks out there to block various other kinds of > change, but I was wondering if anyone had specifically ever written > one to block fast forward merges. How would you detect them? If I do a fast-forward merge, the result is indistinguishable from simply building the commits directly on the branch in the first place. If you mean "nobody should ever build commits directly on master, but always be merging in commits from topic branches", then that is easier to enforce; just look for non-merge commits down the --first-parent line, and reject if you find any. I think you could do it with: git rev-list --max-parents=1 --first-parent $OLD..$NEW If that produces output, then somebody build directly on master (or did a backwards master->topic merge, but if you care about first-parents lineage, then that is equally bad). -Peff ``` ## Neal Kreitzinger, 2012-03-21 20:32 Subject: Re: Has anyone written a hook to block fast forward merges to a branch? Message-ID: <4F6A3ACA.6050100@gmail.com> URL: https://gitlist.dev/e/4F6A3ACA.6050100%40gmail.com In-Reply-To: ``` On 3/21/2012 1:22 PM, Chris Patti wrote: > I know there are hooks out there to block various other kinds of > change, but I was wondering if anyone had specifically ever written > one to block fast forward merges. > Maybe git-merge --no-ff would also be helpful to "do what you want". (I'm not sure why you would tell people they can't do their work really fast or rebase to make it look like they did, but it seems that's what you are also implying.) v/r, neal ``` ## Jeff King, 2012-03-21 20:43 Subject: Re: Has anyone written a hook to block fast forward merges to a branch? Message-ID: <20120321204333.GB15021@sigill.intra.peff.net> URL: https://gitlist.dev/e/20120321204333.GB15021%40sigill.intra.peff.net In-Reply-To: <4F6A3ACA.6050100@gmail.com> ``` On Wed, Mar 21, 2012 at 03:32:10PM -0500, Neal Kreitzinger wrote: > On 3/21/2012 1:22 PM, Chris Patti wrote: > >I know there are hooks out there to block various other kinds of > >change, but I was wondering if anyone had specifically ever written > >one to block fast forward merges. > > > Maybe git-merge --no-ff would also be helpful to "do what you want". When I wrote my response, I assumed the intent was that people _should_ be using --no-ff, but that he wanted to enforce it via hook during a push to a central repository. Reading it again, I'm not sure whether that is the case or not. If not, the disregard my original response. :) -Peff ``` ## Neal Kreitzinger, 2012-03-21 21:14 Subject: Re: Has anyone written a hook to block fast forward merges to a branch? Message-ID: <4F6A44AD.4040600@gmail.com> URL: https://gitlist.dev/e/4F6A44AD.4040600%40gmail.com In-Reply-To: <20120321204333.GB15021@sigill.intra.peff.net> ``` On 3/21/2012 3:43 PM, Jeff King wrote: > On Wed, Mar 21, 2012 at 03:32:10PM -0500, Neal Kreitzinger wrote: > >> On 3/21/2012 1:22 PM, Chris Patti wrote: >>> I know there are hooks out there to block various other kinds of >>> change, but I was wondering if anyone had specifically ever >>> written one to block fast forward merges. >>> >> Maybe git-merge --no-ff would also be helpful to "do what you >> want". > > When I wrote my response, I assumed the intent was that people > _should_ be using --no-ff, but that he wanted to enforce it via hook > during a push to a central repository. > > Reading it again, I'm not sure whether that is the case or not. If > not, the disregard my original response. :) > Would your script only work at "push time", or would it also work at "commit time"? I'm not sure at what point he thinks he wants to enforce it. I don't think git yet knows the info your script is asking for at "commit time" (ie, pre-commit hook and its brethren), and by the time it does know it's too late to block the commit locally. Maybe it does know that inof at the point one of those "commit time" hooks runs. I haven't tried it. v/r, neal ``` ## Jeff King, 2012-03-21 21:22 Subject: Re: Has anyone written a hook to block fast forward merges to a branch? Message-ID: <20120321212201.GA16734@sigill.intra.peff.net> URL: https://gitlist.dev/e/20120321212201.GA16734%40sigill.intra.peff.net In-Reply-To: <4F6A44AD.4040600@gmail.com> ``` On Wed, Mar 21, 2012 at 04:14:21PM -0500, Neal Kreitzinger wrote: > >When I wrote my response, I assumed the intent was that people > >_should_ be using --no-ff, but that he wanted to enforce it via hook > >during a push to a central repository. > > > Would your script only work at "push time", or would it also work at > "commit time"? I'm not sure at what point he thinks he wants to > enforce it. I don't think git yet knows the info your script is > asking for at "commit time" (ie, pre-commit hook and its brethren), > and by the time it does know it's too late to block the commit > locally. Maybe it does know that inof at the point one of those > "commit time" hooks runs. I haven't tried it. Completely untested, but you could probably do something like this in a pre-commit hook: if test "`git symbolic-ref HEAD 2>/dev/null`" = "refs/heads/master" && ! test -e "`git rev-parse --git-dir`/MERGE_HEAD" then echo >&2 "Don't commit right on master. Go make a topic branch." exit 1 fi but I'm not sure if that would catch fast-forward merges or not. You might also have to do an ancestry check against MERGE_HEAD. Whether such a thing would be useful depends on your workflow and exactly what you're trying to achieve. Usually people try to enforce policy like this on pushes, just because that is an easy central point (e.g., somebody who forgets to use topic branches or --no-ff may also forget to set up their hooks; but if you have a central publishing point, it's easy to set up the policies there just once). -Peff ```