Re: [PATCH v3 1/1] Fix gitdir e.g. to respect core.hooksPath

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Pratyush,

On Tue, 8 Oct 2019, Pratyush Yadav wrote:

> Could you please change the commit subject to more clearly state that we
> are caching all paths. This is not something just related to hooks any
> more.

It is related, but not exclusively so. Changed accordingly.

> On 04/10/19 02:41PM, 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.
> >
> > An original patch handled only the hooksPath setting, however, during
> > the code submission it was deemed better to fix all call to the `gitdir`
> > function.
> >
> > To avoid spawning a gazillion `git rev-parse --git-path` instances, we
> > cache the returned paths, priming the cache upon startup in a single
> > `git rev-parse invocation` with the known entries.
>
> I think it would also be a good idea to mention that we are fixing
> worktree paths not being correct.

Done.

> > 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 | 52 +++++++++++++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 49 insertions(+), 3 deletions(-)
> >
> > diff --git a/git-gui.sh b/git-gui.sh
> > index fd476b6999..8b72e59cd0 100755
> > --- a/git-gui.sh
> > +++ b/git-gui.sh
> > @@ -158,6 +158,7 @@ if {[tk windowingsystem] eq "aqua"} {
> >
> >  set _appname {Git Gui}
> >  set _gitdir {}
> > +array set _gitdir_cache {}
> >  set _gitworktree {}
> >  set _isbare {}
> >  set _gitexec {}
> > @@ -197,12 +198,57 @@ proc appname {} {
> >  	return $_appname
> >  }
> >
> > +proc prime_gitdir_cache {} {
> > +	global _gitdir _gitdir_cache
> > +
> > +	set gitdir_cmd [list git rev-parse --git-dir]
> > +
> > +	# `--git-path` is only supported since Git v2.5.0
> > +	if {[package vcompare $::_git_version 2.5.0] >= 0} {
>
> I think we should mention the source of the list of "magic" keys. A
> comment mentioning this list came from looking at the common calls to
> `gitdir` in the rest of the git-gui code would explain this function to
> a future reader better.

Makes sense.

> > +		set gitdir_keys [list \
> > +			CHERRY_PICK_HEAD FETCH_HEAD GITGUI_BCK GITGUI_EDITMSG \
> > +			GITGUI_MSG HEAD hooks hooks/prepare-commit-msg \
> > +			index.lock info info/exclude logs MERGE_HEAD MERGE_MSG \
> > +			MERGE_RR objects "objects/4\[0-1\]/*" \
> > +			"objects/4\[0-3\]/*" objects/info \
> > +			objects/info/alternates objects/pack packed-refs \
> > +			PREPARE_COMMIT_MSG rebase-merge/head-name remotes \
> > +			rr-cache rr-cache/MERGE_RR SQUASH_MSG \
> > +		]
> > +
> > +		foreach key $gitdir_keys {
> > +			lappend gitdir_cmd --git-path $key
> > +		}
> > +	}
> > +
> > +	set i -1
> > +	foreach path [split [eval $gitdir_cmd] "\n"] {
>
> A call to the procedure 'git' is wrapped in a 'catch' in a lot of
> places. But it is also not wrapped in 'catch' in a lot of other places.
>
> I'm not sure how something like this would fail, so I'm not sure if
> wrapping this call in a catch is a good idea. But it is something to
> consider.

If that call fails, we lack a `gitdir`, which is a rather fundamental
prerequisite to running Git GUI. I'd rather show an (ugly, but also
highly unexpected) exception.

In other words, I think the patch should stay "catch-less".

> > +		if {$i eq -1} {
> > +			set _gitdir $path
> > +		} else {
> > +			set _gitdir_cache([lindex $gitdir_keys $i]) $path
> > +		}
> > +		incr i
> > +	}
> > +}
> > +
> >  proc gitdir {args} {
> > -	global _gitdir
> > +	global _gitdir _gitdir_cache
> > +
> >  	if {$args eq {}} {
> >  		return $_gitdir
> >  	}
> > -	return [eval [list file join $_gitdir] $args]
> > +
> > +	set args [eval [list file join] $args]
> > +	if {![info exists _gitdir_cache($args)]} {
> > +		if {[package vcompare $::_git_version 2.5.0] >= 0} {
> > +			set _gitdir_cache($args) [git rev-parse --git-path $args]
> > +		} else {
> > +			set _gitdir_cache($args) [file join $_gitdir $args]
> > +		}
> > +	}
> > +
> > +	return $_gitdir_cache($args)
> >  }
> >
> >  proc gitexec {args} {
> > @@ -1242,7 +1288,7 @@ if {[catch {
> >  	&& [catch {
> >  		# beware that from the .git dir this sets _gitdir to .
> >  		# and _prefix to the empty string
> > -		set _gitdir [git rev-parse --git-dir]
> > +		prime_gitdir_cache
> >  		set _prefix [git rev-parse --show-prefix]
> >  	} err]} {
> >  	load_config 1
>
> Can these paths we cache change while git-gui is running, say by a
> command run by the user in the terminal? In that case, we should refresh
> the list when the user rescans.

I guess it can. A user could configure `core.hooksPath` while Git GUI is
open, after all. Or rewrite the `.git` file of a worktree.

I won't touch the `.git` file part, but I changed the `rescan` code to
re-prime the gitdir cache.

Thanks for the review,
Johannes

>
> Other than some minor comments, looks good. Thanks.
>
> --
> Regards,
> Pratyush Yadav
>