Re: [RFC/PATCH v2 3/3] Add 'update-branch' hook

From: Felipe Contreras <felipe.contreras@gmail.com>
Date: Apr 23, 2014, 21:08 UTC
Message-ID: <53582bb6ceb64_24448772ecaf@nysa.notmuch>
In-Reply-To: <xmqqsip3yemg.fsf@gitster.dls.corp.google.com>

Junio C Hamano wrote:

Show 20 quoted lines

> Felipe Contreras <felipe.contreras@gmail.com> writes:
> 
> > This hook is invoked before a branch is updated, either when a branch is
> > created or updated with 'git branch', or when it's rebased with 'git
> > rebase'.  It receives three parameters; the name of the branch, the
> > SHA-1 of the latest commit, and the SHA-1 of the first commit of the
> > branch.
> >
> > When a branch is created the first and last commits of the branch are
> > the same, however when a branch is rebased they are not. If the SHA-1 of
> > the first commit of the branch is not available (e.g. git reset) a null
> > SHA-1 (40 zeroes) would be passed.
> >
> > The hook exit status can be used to deny the branch update.
> >
> > It can be used to verify the validity of branch names, and also to keep
> > track of the origin point of a branch, which is otherwise not possible
> > to find out [1].
> 
> Please call it pre-update-branch at least,

I will do so when I see a good argument for it.

> unless you want to make sure that time spent on others in the discussion
> thread for the previous round becomes wasted.

Unless you want to make sure the time *I* spent in the discussion is wasted.

I'm still waiting for replies to my last arguments.

Show 7 quoted lines

> > +update-branch
> > +~~~~~~~~~~~~~
> > +
> > +This hook is invoked before a branch is updated, either when a branch is
> > +created or updated with 'git branch', or when it's rebased with 'git rebase'.
> 
> Does "git checkout -B aBranch" count?

Yes.

> Does "git reset $there" count?

Yes.

Show 17 quoted lines

> I guess "git commit" or "git merge" on a branch to advance its tip
> in a usual way would not count (and I can think of good reasons why
> they should not count), but it is only a weak "guess".  The above
> two lines does not give readers enough hint to determine if "branch
> and rebase will be the only two and no other command will ever
> trigger" or "branch and rebase are only examples---for others, guess
> on your own" (and if the latter, enough clue to use in guessing).
> I cannot guess if "git fetch $there $that:refs/heads/master" should
> trigger the hook, for example.
> 
> To put it another way.
> 
> How does one, who is adding a new command that causes a branch tip
> to be updated, to decide if it should trigger this hook?  What are
> the common things among commands that can update branch tips that
> this hook gets called that are missing from commands that update
> branch tips that this hook does not get called?

I guess the guideline should be: if the branch is clearly moving forward the hook is not called, if the branch is manually changed in any way, it should.

This omits non-porcelain commands, such as update-ref. I don't think those should trigger the hook.

-- 
Felipe Contreras