[PATCH v2 5/6] setup: teach discover_git_directory to respect the commondir

[Brandon Williams <bmwill@google.com>]

Currently 'discover_git_directory' only looks at the gitdir to determine
if a git directory was discovered.  This causes a problem in the event
that the gitdir which was discovered was in fact a per-worktree git
directory and not the common git directory.  This is because the
repository config, which is checked to verify the repository's format,
is stored in the commondir and not in the per-worktree gitdir.  Correct
this behavior by checking the config stored in the commondir.

It will also be of use for callers to have access to the commondir, so
lets also return that upon successfully discovering a git directory.

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 cache.h  |  3 ++-
 config.c | 10 ++++++----
 setup.c  |  9 +++++++--
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/cache.h b/cache.h
index fd45b8c55..a4176436d 100644
--- a/cache.h
+++ b/cache.h
@@ -530,7 +530,8 @@ extern void setup_work_tree(void);
  * appended to gitdir. The return value is either NULL if no repository was
  * found, or pointing to the path inside gitdir's buffer.
  */
-extern const char *discover_git_directory(struct strbuf *gitdir);
+extern const char *discover_git_directory(struct strbuf *commondir,
+					  struct strbuf *gitdir);
 extern const char *setup_git_directory_gently(int *);
 extern const char *setup_git_directory(void);
 extern char *prefix_path(const char *prefix, int len, const char *path);
diff --git a/config.c b/config.c
index 4e2842689..9aa9b9715 100644
--- a/config.c
+++ b/config.c
@@ -1652,7 +1652,8 @@ static void configset_iter(struct config_set *cs, config_fn_t fn, void *data)
 void read_early_config(config_fn_t cb, void *data)
 {
 	struct config_options opts = {0};
-	struct strbuf buf = STRBUF_INIT;
+	struct strbuf commondir = STRBUF_INIT;
+	struct strbuf gitdir = STRBUF_INIT;
 
 	opts.respect_includes = 1;
 
@@ -1666,12 +1667,13 @@ void read_early_config(config_fn_t cb, void *data)
 	 * notably, the current working directory is still the same after the
 	 * call).
 	 */
-	else if (discover_git_directory(&buf))
-		opts.git_dir = buf.buf;
+	else if (discover_git_directory(&commondir, &gitdir))
+		opts.git_dir = gitdir.buf;
 
 	git_config_with_options(cb, data, NULL, &opts);
 
-	strbuf_release(&buf);
+	strbuf_release(&commondir);
+	strbuf_release(&gitdir);
 }
 
 static void git_config_check_init(void);
diff --git a/setup.c b/setup.c
index e99a82cbe..7bbb8736f 100644
--- a/setup.c
+++ b/setup.c
@@ -946,10 +946,12 @@ static enum discovery_result setup_git_directory_gently_1(struct strbuf *dir,
 	}
 }
 
-const char *discover_git_directory(struct strbuf *gitdir)
+const char *discover_git_directory(struct strbuf *commondir,
+				   struct strbuf *gitdir)
 {
 	struct strbuf dir = STRBUF_INIT, err = STRBUF_INIT;
 	size_t gitdir_offset = gitdir->len, cwd_len;
+	size_t commondir_offset = commondir->len;
 	struct repository_format candidate;
 
 	if (strbuf_getcwd(&dir))
@@ -974,8 +976,10 @@ const char *discover_git_directory(struct strbuf *gitdir)
 		strbuf_insert(gitdir, gitdir_offset, dir.buf, dir.len);
 	}
 
+	get_common_dir(commondir, gitdir->buf + gitdir_offset);
+
 	strbuf_reset(&dir);
-	strbuf_addf(&dir, "%s/config", gitdir->buf + gitdir_offset);
+	strbuf_addf(&dir, "%s/config", commondir->buf + commondir_offset);
 	read_repository_format(&candidate, dir.buf);
 	strbuf_release(&dir);
 
@@ -983,6 +987,7 @@ const char *discover_git_directory(struct strbuf *gitdir)
 		warning("ignoring git dir '%s': %s",
 			gitdir->buf + gitdir_offset, err.buf);
 		strbuf_release(&err);
+		strbuf_setlen(commondir, commondir_offset);
 		return NULL;
 	}
 
-- 
2.13.1.518.g3df882009-goog