Re: [PATCH 1/1] respect core.hooksPath, falling back to .git/hooks

[Pratyush Yadav <me@yadavpratyush.com>]

On 27/09/19 08:10AM, Bert Wesarg wrote:
> On Fri, Sep 27, 2019 at 12:40 AM Pratyush Yadav <me@yadavpratyush.com> wrote:
> >
> > Hi,
> >
> > On 26/09/19 02:17PM, Johannes Schindelin via GitGitGadget wrote:
> > > From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> > >
> > > Since v2.9.0, Git knows about the config variable core.hookspath
> > > that allows overriding the path to the directory containing the
> > > Git hooks.
> > >
> > > Since v2.10.0, the `--git-path` option respects that config
> > > variable, too, so we may just as well use that command.
> > >
> > > For Git versions older than v2.5.0 (which was the first version to
> > > support the `--git-path` option for the `rev-parse` command), we
> > > simply fall back to the previous code.
> > >
> > > This fixes https://github.com/git-for-windows/git/issues/1755
> > >
> > > Initial-patch-by: Philipp Gortan <philipp@gortan.org>
> > > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > > ---
> > >  git-gui.sh | 6 +++++-
> > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/git-gui.sh b/git-gui.sh
> > > index fd476b6999..b2c6e7a1db 100755
> > > --- a/git-gui.sh
> > > +++ b/git-gui.sh
> > > @@ -623,7 +623,11 @@ proc git_write {args} {
> > >  }
> > >
> > >  proc githook_read {hook_name args} {
> > > -     set pchook [gitdir hooks $hook_name]
> > > +     if {[package vcompare $::_git_version 2.5.0] >= 0} {
> > > +             set pchook [git rev-parse --git-path "hooks/$hook_name"]
> > > +     } else {
> > > +             set pchook [gitdir hooks $hook_name]
> > > +     }
> >
> > gitdir is used in a lot of places, and I think all those would also
> > benefit from using --git-path. So I think it is a better idea to move
> > this to the procedure gitdir. It would have to be refactored to take any
> > number of arguments, instead of the two it takes here.
> 
> gitdir already takes an arbitrary number of arguments and joins them
> to a path. The more imminent challenge is, that gitdir caches the
> GIT_DIR, thus it tries to avoid calling "git rev-parse". Which works
> for most, but not for hooks.

What I was thinking of was something like this:

  - If no args are passed, then just directly return $_gitdir. This is 
    already being done. I assume the GIT_DIR relocation is already 
    handled by `git rev-parse --git-dir`, so this would point to the 
    correct location.
  - If args are passed, then we want a subdirectory of GIT_DIR In this 
    case, it is possible that this subdirectory has also been relocated 
    (hooks/ being one of those subdirectories). So in this case, use 
    `git rev-parse --git-path` instead.

So the gitdir procedure would look something like:

  proc gitdir {args} {
  	global $_gitdir
  	if {$args eq {}} {
  		# Return the cached GIT_DIR
  		return $_gitdir
  	}
  
  	# Use `git rev-parse --git-path` to get the path instead of 
  	# using the cached value.
  }

Am I missing something? Or does this fix the issue you describe?
 
> We could either maintain a blacklist, for what we cache the result
> too, or always call "git rev-parse --git-dir".
> 
> This blacklist would need to be in sync with the one in Git's
> path.c::adjust_git_path() than.

Is caching GIT_DIR that important in terms of performance? Otherwise, 
I'd say calling `git rev-parse --git-path` for _every_ subdirectory of 
GIT_DIR is a much simpler solution.

-- 
Regards,
Pratyush Yadav