Subject: Re: [PATCH v3 2/2] git_path(): handle `.lock` files correctly

From: SZEDER Gábor <[email-masked]>
Date: Tue, 22 Oct 2019 18:01:05 +0200

On Mon, Oct 21, 2019 at 09:54:42PM +0000, Johannes Schindelin via GitGitGadget wrote:
> From: Johannes Schindelin <[email-masked]>
> 
> Ever since worktrees were introduced, the `git_path()` function _really_
> needed to be called e.g. to get at the path to `logs/HEAD` (`HEAD` is
> specific to the worktree, and therefore so is its reflog). However, the
> wrong path is returned for `logs/HEAD.lock`.
> 
> This does not matter as long as the Git executable is doing the asking,
> as the path for that `logs/HEAD.lock` file is constructed from
> `git_path("logs/HEAD")` 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). While it does
> not seem as if Git GUI in particular is asking for `logs/HEAD.lock`,
> let's be safe rather than sorry.
> 
> Side note: Git GUI _does_ ask for `index.lock`, but that is already
> resolved correctly, due to `update_common_dir()` preferring to leave
> unknown paths in the (worktree-specific) git directory.
> 
> Signed-off-by: Johannes Schindelin <[email-masked]>
> ---
>  path.c               |  8 +++++++-
>  t/t1500-rev-parse.sh | 15 +++++++++++++++
>  2 files changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/path.c b/path.c
> index e3da1f3c4e..5ff64e7a8a 100644
> --- a/path.c
> +++ b/path.c
> @@ -349,10 +349,16 @@ static int check_common(const char *unmatched, void *value, void *baton)
>  static void update_common_dir(struct strbuf *buf, int git_dir_len,
>  			      const char *common_dir)
>  {
> -	char *base = buf->buf + git_dir_len;
> +	char *base = buf->buf + git_dir_len, *base2 = NULL;
> +
> +	if (ends_with(base, ".lock"))
> +		base = base2 = xstrndup(base, strlen(base) - 5);

Hm, this adds the magic number 5 and calls strlen(base) twice, because
ends_with() calls strip_suffix(), which calls strlen().  Calling
strip_suffix() directly would allow us to avoid the magic number and
the second strlen():

  size_t len;
  if (strip_suffix(base, ".lock", &len))
          base = base2 = xstrndup(base, len);

>  	init_common_trie();
>  	if (trie_find(&common_trie, base, check_common, NULL) > 0)
>  		replace_dir(buf, git_dir_len, common_dir);
> +
> +	free(base2);
>  }
>  
>  void report_linked_checkout_garbage(void)
> 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
> +'

I think this test better fits into 't0060-path-utils.sh': it already
checks 'logs/HEAD' and 'index' in a different working tree (well, with
GIT_COMMON_DIR set, but that's the same), and it has a helper function
to make each of the two new .lock tests a one-liner.

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