[PATCH v4 2/2] git_path(): handle `.lock` files correctly

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

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 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 <johannes.schindelin@gmx.de>
---
 path.c                | 6 ++++++
 t/t0060-path-utils.sh | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/path.c b/path.c
index e3da1f3c4e..198a867017 100644
--- a/path.c
+++ b/path.c
@@ -11,6 +11,7 @@
 #include "path.h"
 #include "packfile.h"
 #include "object-store.h"
+#include "lockfile.h"
 
 static int get_st_mode_bits(const char *path, int *mode)
 {
@@ -350,9 +351,14 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len,
 			      const char *common_dir)
 {
 	char *base = buf->buf + git_dir_len;
+	int has_lock_suffix = strbuf_strip_suffix(buf, LOCK_SUFFIX);
+
 	init_common_trie();
 	if (trie_find(&common_trie, base, check_common, NULL) > 0)
 		replace_dir(buf, git_dir_len, common_dir);
+
+	if (has_lock_suffix)
+		strbuf_addstr(buf, LOCK_SUFFIX);
 }
 
 void report_linked_checkout_garbage(void)
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index c7b53e494b..2aca8ccff9 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -285,8 +285,10 @@ test_git_path GIT_OBJECT_DIRECTORY=foo objects/foo foo/foo
 test_git_path GIT_OBJECT_DIRECTORY=foo objects2 .git/objects2
 test_expect_success 'setup common repository' 'git --git-dir=bar init'
 test_git_path GIT_COMMON_DIR=bar index                    .git/index
+test_git_path GIT_COMMON_DIR=bar index.lock               .git/index.lock
 test_git_path GIT_COMMON_DIR=bar HEAD                     .git/HEAD
 test_git_path GIT_COMMON_DIR=bar logs/HEAD                .git/logs/HEAD
+test_git_path GIT_COMMON_DIR=bar logs/HEAD.lock           .git/logs/HEAD.lock
 test_git_path GIT_COMMON_DIR=bar logs/refs/bisect/foo     .git/logs/refs/bisect/foo
 test_git_path GIT_COMMON_DIR=bar logs/refs/bisec/foo      bar/logs/refs/bisec/foo
 test_git_path GIT_COMMON_DIR=bar logs/refs/bisec          bar/logs/refs/bisec
-- 
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