[PATCH v3 0/2] Handle git_path() with lock files correctly in worktrees

I stumbled over this during my recent work in Git GUI [https://github.com/gitgitgadget/git/pull/361] that was originally really only intended to use the correct hooks directory.

It turns out that my fears that index.lock was mishandled were unfounded, hence this patch series has a lot lower priority for me than "OMG we must push this into v2.24.0!".

Technically, the first patch is not needed (because I decided against adding a test to t1400 in the end, in favor of t1500), but it shouldn't hurt, either.

Changes since v2:

 * Adjusted the commit message to really not talk about index.lock.
 * Instead of modifying the code inside trie_find() to special-case .lock, I
   now copy the string without the suffix .lock (if any) before handing it
   off to trie_find().

Changes since v1:

 * Clarified the commit message to state that index.lock is fine, it is 
   logs/HEAD.lock that isn't.

Johannes Schindelin (2):
  t1400: wrap setup code in test case
  git_path(): handle `.lock` files correctly

 path.c                |  8 +++++++-
 t/t1400-update-ref.sh | 18 ++++++++++--------
 t/t1500-rev-parse.sh  | 15 +++++++++++++++
 3 files changed, 32 insertions(+), 9 deletions(-)

base-commit: 108b97dc372828f0e72e56bbb40cae8e1e83ece6
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-401%2Fdscho%2Flock-files-in-worktrees-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-401/dscho/lock-files-in-worktrees-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/401

Range-diff vs v2:

 1:  cf97c5182e = 1:  cf97c5182e t1400: wrap setup code in test case
 2:  93dba5a3a3 ! 2:  8b1f4f089a git_path(): handle `.lock` files correctly
     @@ -4,12 +4,12 @@
      
          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). However, the wrong path is returned for
     -    `logs/HEAD.lock`.
     +    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 `index.lock` file is constructed from
     -    `git_path("index")` by appending the `.lock` suffix.
     +    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
     @@ -19,7 +19,8 @@
          let's be safe rather than sorry.
      
          Side note: Git GUI _does_ ask for `index.lock`, but that is already
     -    resolved correctly.
     +    resolved correctly, due to `update_common_dir()` preferring to leave
     +    unknown paths in the (worktree-specific) git directory.
      
          Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
      
     @@ -27,23 +28,23 @@
       --- a/path.c
       +++ b/path.c
      @@
     - 	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);
     -@@
     - 
     - 	/* Matched the entire compressed section */
     - 	key += i;
     --	if (!*key)
     -+	if (!*key || !strcmp(key, ".lock"))
     - 		/* End of key */
     - 		return fn(key, root->value, 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);
     ++
     + 	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
       --- a/t/t1500-rev-parse.sh