Re: [PATCH 2/2] git_path(): handle `.lock` files correctly

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

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Hi Gábor,

On Wed, 16 Oct 2019, SZEDER Gábor wrote:

> On Wed, Oct 16, 2019 at 07:07:17AM +0000, Johannes Schindelin via GitGitGadget wrote:
> > From: Johannes Schindelin <johannes.schindelin@gmx.de>
> >
> > Ever since worktrees were introduced, the `git_path()` function _really_
> > needed to be called e.g. to get at the `index`. However, the wrong path
> > is returned for `index.lock`.
>
> Could you give an example where it returns the wrong path for
> 'index.lock'?

Oh wow, this was a left-over from an early draft, before I got the
regression test to work... What I meant was of course logs/HEAD.lock.
Will fix.

> I tried to reproduce this issue in a working tree, but
> no matter what I've tried, 'git rev-parse --git-dir index.lock' always
> returned the right path.

With `s/--git-dir/--git-path/`, I agree.

> > This does not matter as long as the Git executable is doing the asking,
> > as the path for that `index.lock` file is constructed from
> > `git_path("index")` by appending the `.lock` suffix.
> >
> > However, Git GUI just learned to use `--git-path` instead of appending
> > relative paths to what `git rev-parse --git-dir` returns (and as a
> > consequence not only using the correct hooks directory, but also using
> > the correct paths in worktrees other than the main one). And one of the
> > paths it is looking for is... you guessed it... `index.lock`.
> >
> > So let's make that work as script writers would expect it to.
> >
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> >  path.c               |  4 ++--
> >  t/t1500-rev-parse.sh | 15 +++++++++++++++
> >  2 files changed, 17 insertions(+), 2 deletions(-)
> >
> > diff --git a/path.c b/path.c
> > index e3da1f3c4e..ff85692b45 100644
> > --- a/path.c
> > +++ b/path.c
> > @@ -268,7 +268,7 @@ static int trie_find(struct trie *root, const char *key, match_fn fn,
> >  	int result;
> >  	struct trie *child;
> >
> > -	if (!*key) {
> > +	if (!*key || !strcmp(key, ".lock")) {
> >  		/* we have reached the end of the key */
> >  		if (root->value && !root->len)
> >  			return fn(key, root->value, baton);
> > @@ -288,7 +288,7 @@ static int trie_find(struct trie *root, const char *key, match_fn fn,
> >
> >  	/* Matched the entire compressed section */
> >  	key += i;
> > -	if (!*key)
> > +	if (!*key || !strcmp(key, ".lock"))
> >  		/* End of key */
> >  		return fn(key, root->value, baton);
> >
> > diff --git a/t/t1500-rev-parse.sh b/t/t1500-rev-parse.sh
> > index 01abee533d..d318a1eeef 100755
> > --- a/t/t1500-rev-parse.sh
> > +++ b/t/t1500-rev-parse.sh
> > @@ -116,6 +116,21 @@ test_expect_success 'git-path inside sub-dir' '
> >  	test_cmp expect actual
> >  '
> >
> > +test_expect_success 'git-path in worktree' '
> > +	test_tick &&
> > +	git commit --allow-empty -m empty &&
> > +	git worktree add --detach wt &&
> > +	test_write_lines >expect \
> > +		"$(pwd)/.git/worktrees/wt/logs/HEAD" \
> > +		"$(pwd)/.git/worktrees/wt/logs/HEAD.lock" \
> > +		"$(pwd)/.git/worktrees/wt/index" \
> > +		"$(pwd)/.git/worktrees/wt/index.lock" &&
> > +	git -C wt rev-parse >actual \
> > +		--git-path logs/HEAD --git-path logs/HEAD.lock \
> > +		--git-path index --git-path index.lock &&
> > +	test_cmp expect actual
>
> Without the fix applied this test fails with:
>
>   + test_cmp expect actual
>   --- expect      2019-10-16 10:20:31.047229423 +0000
>   +++ actual      2019-10-16 10:20:31.051229519 +0000
>   @@ -1,4 +1,4 @@
>    /home/szeder/src/git/t/trash directory.t1500-rev-parse/.git/worktrees/wt/logs/HEAD
>   -/home/szeder/src/git/t/trash directory.t1500-rev-parse/.git/worktrees/wt/logs/HEAD.lock
>   +/home/szeder/src/git/t/trash directory.t1500-rev-parse/.git/logs/HEAD.lock
>    /home/szeder/src/git/t/trash directory.t1500-rev-parse/.git/worktrees/wt/index
>    /home/szeder/src/git/t/trash directory.t1500-rev-parse/.git/worktrees/wt/index.lock
>   error: last command exited with $?=1
>
> So the path of 'index.lock' seems to be fine already, it's the path of
> the lockfile for HEAD's reflog that's indeed wrong and makes the test
> fail.

Indeed, and this makes this patch much less important than I previosly
thought. It's not like it would break Git GUI in worktrees, which is
what I thought, which in turn is the reason I sent this so close to
-rc0.

> On a related note, I'm not sure whether the path of the reflogs
> directory is right while in a different working tree...  Both with and
> without this patch I get a path pointing to the main working tree:
>
>   $ ./git -C WT/ rev-parse --git-path logs
>   /home/szeder/src/git/.git/logs
>
> However, I'm not sure what the right path should be in the first
> place, given that each working tree has its own 'logs' directory, but
> only for HEAD's reflog, while everything else goes to the main working
> tree's 'logs' directory.

It's like Junio said, the reflog for `HEAD` is special because `HEAD` is
special. Look for `common_list` in `path.c` (it is a bit confusing, I
admit, you have to look for the 3rd column of numbers: if it is a `1`,
then it is a worktree-specific path, if it is `0`, it is supposed to
live in the "commondir", i.e. in the gitdir of the main worktree).

Thanks,
Dscho

>
> > +'
> > +
> >  test_expect_success 'rev-parse --is-shallow-repository in shallow repo' '
> >  	test_commit test_commit &&
> >  	echo true >expect &&
> > --
> > gitgitgadget
>