On Wed, Jul 29, 2015 at 6:37 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote: > Johan Herland <johan@xxxxxxxxxxx> writes: >> On Wed, Jul 29, 2015 at 7:01 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote: >>> Johan Herland <johan@xxxxxxxxxxx> writes: >>> >>>> I believe it is a bad compromise. It complicates the code, and it >>>> provides a concurrent notes merges that is unnecessarily tied to (and >>>> dependent on) worktrees. For example, if I wanted to perform N >>>> concurrent notes merges in a project that happens to have a huge >>>> worktree, I would now have to create N copies of the huge worktree... >>> >>> Who said worktree has to be populated? You should be able to have >>> an absolutely empty checkout just like "clone --no-checkout". >> >> IMHO that's an insane workaround that only serves to highlight the >> conceptual problems of binding notes merges (as they are implemented >> today) to worktrees. > > Actually, the name "linked worktree" is probably a misnomer. > > There is nothing fundamental in the mechanism or in the concept that > says that these multiple $GIT_DIR's must not be a bare one. The > main thing the separation between $GIT_DIR and $GIT_COMMON_DIR > affords you is that you can have some things shared across them > (e.g. refs/*, objects) while making others per $GIT_DIR (e.g. HEAD, > index, etc.). > > With that in mind, it is not an insane workaround but a very natural > mechanism suited exactly for what you want to do: using a feature > (e.g. "notes merge") that currently can have at most one instance > running at a time because it stores its state inside $GIT_DIR, and > you want to have N concurrent one going. You keep that "state per > running instance" inside $GIT_DIR (i.e. not shared) and use the > "linked worktree" mechanism to have multiple $GIT_DIR, connected > to the same $GIT_COMMON_DIR. Makes sense, although currently, IINM, those multiple $GIT_DIRs must be associated with strictly different branches, which is completely unrelated to the desired notes-merge restriction (which applies to notes refs - not branches). But this has been discussed to death, already. >> But, whatever. This is unrelated to David's current effort, and I >> don't want to hold that up, so please move along, nothing to see here. > > I need this part from an earlier message answered to unblock David's > topic: > > Now we are getting somewhere. So is there more that is needed > than separating NOTES_MERGE_REF per worktree to make this work > (remember, multiple notes-merge in a single worktree is a > non-goal, just like multiple merge in a single worktree is not > supported today and will not be)? Is there some other state > that is not captured by NOTES_MERGE_REF and friends that you > would end up recording a wrong merge result, if two worktrees > that have NOTES_MERGE_REF pointing at a different ref in > refs/notes/* try to do the notes-merge at the same time? I believe the answer to both questions is "No". > If we do not change anything (not even applying the "[PATCH] notes: handle multiple worktrees" patch > we are discussing), all these things prefixed with NOTES_ will > become per $GIT_DIR with linked worktrees. > > NOTES_EDITMSG, NOTES_MERGE_REF, NOTES_MERGE_PARTIAL, > NOTES_MERGE_WORKTREE > > The user could attempt to start different notes merges in her > multiple $GIT_DIRs. The question is to what degree we want to > support her. > > Is it sufficient to have these per $GIT_DIR, when the user has two > $GIT_DIRs connected to the same repository and wants to do two > "notes merge" acting on different ref in refs/notes/*? Or are there > some other states in the shared part kept, which would be stomped on > by simultaneously running "notes merge" instances in different > $GIT_DIRs, that make this not to work? Any other problems in the > remainder of the current implementation of "notes merge"? Still, I believe the answer is "No". > If there are reasons/limitations that make simultaneous "notes > merge" of different notes in different $GIT_DIRs impossible, then I > agree we shouldn't bother with "[PATCH] notes: handle multiple worktrees" patch. We should just > declare "do not do it, it does not (yet) work". > > But if there isn't, "[PATCH] notes: handle multiple worktrees" is the absolute minimum thing we could > do to make "notes merge" usable by making sure that the user does > not attempt merging the same refs/notes/commits in two different > places. Sure. There's no point in delaying a patch that works well in practice just because I have a delusion of a theoretically cleaner solution that won't make any difference in practice. ...Johan -- Johan Herland, <johan@xxxxxxxxxxx> www.herland.net -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html