Re: [PATCH 0/3] pre-merge-hook
Junio C Hamano venit, vidit, dixit 06.09.2012 20:34:
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> Michael J Gruber <git@drmicha.warpmail.net> writes:
>
>> Junio C Hamano venit, vidit, dixit 06.09.2012 07:07:
>>> Michael J Gruber <git@drmicha.warpmail.net> writes:
>>>
>>>> The pre-commit hook is often used to ensure certain properties
>>>> of each comitted tree like formatting or coding standards,
>>>> validity (lint/make) or code quality (make test). But merges
>>>> introduce new commits unless they are fast forwards, and
>>>> therefore they can break these properties because the
>>>> pre-commit hook is not run by "git merge".
>>>>
>>>> Introduce a pre-merge hook which works for (non ff, automatic)
>>>> merges like pre-commit does for commits. Typically this will
>>>> just call the pre-commit hook (like in the sample hook), but it
>>>> does not need to.
>>>
>>> When your merge asks for a help from you to resolve conflict,
>>> you conclude with "git commit", and at that point, pre-commit
>>> hook will have a chance to reject it, presumably. That means for
>>> any project that wants to audit a merge via hook, their
>>> pre-commit hook MUST be prepared to look at and judge a merge.
>>> Given that, is a separate hook that "can just call the pre-commit
>>> but does not need to" really needed and useful?
>>>
>>> I admit that I haven't thought things through, but adding a
>>> boolean "merge.usePreCommitHook" smells like a more appropriate
>>> approach to me.
>>>
>>> I dunno.
>>
>> That would be an option ;)
>
> I said "I dunno" as others may have opinions on the best direction to
> go.
Sure. I meant to make a pun the config option approach being an option.
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>> Either works for me, and if we don't change the current behaviour
>> (pre-commit-hook resp. no hook for non-automatic merges resp.
>> automatic merges) the config option is probably less confusing.
>
> If we were to go in the "pre-commit has to be prepared to vet a merge
> already, so let it handle the automerge case" direction, I have
> another suggestion.
>
> Because you need to support "merge --no-verify" to override the hook
> anyway, I think it makes sense to introduce "merge --verify" to force
> it trigger the hook (and it needs to percolate up to "pull").
>
> People who want it always on may want a boolean merge.verify, but
> that should come in a separate step. The patch that implements it
> must make sure all our internal uses of "merge" is updated to pass
> "--no-verify", unless there is a very good reason.
Hmm. Nothing calls cmd_merge() nor the relevant parts. "git pull" calls "git merge" and should probably obey that option. All others (am etc.) call git-merge-${strategy} directly and are not affected by the option. Am I overlooking something?
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> Another direction to go would be to deprecate the "commit is the way
> to conclude a merge that stopped in the middle due to a conflict
> asking for your help" and introduce "merge --continue" [*1*]. That
> would open a way to a separate "pre/post-merge" hook much cleanly. At
> that point it would be clear that "pre-commit" won't be involved in
> "merge" (i.e. the user never will use "git commit" when merging).
>
> I am fairly negative on the current mess imposed on "git commit" that
> has to know who called it and behave differently (look for "whence"
> in builtin/commit.c), and would rather not to see it made worse by
> piling "call pre-merge if exists and in a merge, or call pre-commit"
> kind of hack on top of it.
That is a mess, yes. Part of it is due to the fact that both builtin/{commit,merge}.c do a lot of "commit stuff" in parallel, often with copy & pasted code, and "commit" needs to be aware of other states (in-am, in-rebase) also.
My feeling is that builtin/merge.c should rather get rid of the stuff that parallels things that builtin/commit.c does, so that all is in one place. (I think that redundancy is to blame for the inconsistent hook behaviour for merges even within builtin/merge.c).
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> [Footnote]
>
> *1* This has been brought up a few times during discussion on
> sequencer and mergy operations, and I think it makes sense in the
> longer term. "am" and "rebase" were first to use "--continue",
> instead of having the user to use "commit" to conclude, and later
> "cherry-pick" and "revert" have been updated to follow suit, so
> "merge" may be the only oddball remaining now.
"git merge --continue" to commit a resolved merge, but code-wise builtin/commit.c taking over because it's just one more case?
I afraid that restructuring is beyond my available Git capacity and my self-imposed constraint to avoid anything with backwards compatibility or migration plan issues. (I took this up because I thought it's within, to share something I've been using for a while.)
I fully agree that a big-picture-solution is preferable.
Michael
Michael J Gruber
