git/worktree-config.patch

diff --git a/builtin/config.c b/builtin/config.c
index 7f6c25d..5065d70 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -538,6 +538,10 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		config_options.respect_includes = !given_config_source.file;
 	else
 		config_options.respect_includes = respect_includes_opt;
+	if (!nongit) {
+		config_options.commondir = get_git_common_dir();
+		config_options.git_dir = get_git_dir();
+	}
 
 	if (end_null) {
 		term = '\0';
diff --git a/cache.h b/cache.h
index c1041cc..804bb6c 100644
--- a/cache.h
+++ b/cache.h
@@ -525,12 +525,15 @@ extern void set_git_work_tree(const char *tree);
 
 extern void setup_work_tree(void);
 /*
- * Find GIT_DIR of the repository that contains the current working directory,
- * without changing the working directory or other global state. The result is
- * 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);
+ * Find the commondir and gitdir of the repository that contains the current
+ * working directory, without changing the working directory or other global
+ * state. The result is appended to commondir and gitdir.  If the discovered
+ * gitdir does not correspond to a worktree, then 'commondir' and 'gitdir' will
+ * both have the same result appended to the buffer.  The return value is
+ * either 0 upon success and non-zero if no repository was found.
+ */
+extern int 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);
@@ -1908,6 +1911,7 @@ enum config_origin_type {
 
 struct config_options {
 	unsigned int respect_includes : 1;
+	const char *commondir;
 	const char *git_dir;
 };
 
diff --git a/config.c b/config.c
index f0511e5..54f869a 100644
--- a/config.c
+++ b/config.c
@@ -217,8 +217,6 @@ static int include_by_gitdir(const struct config_options *opts,
 
 	if (opts->git_dir)
 		git_dir = opts->git_dir;
-	else if (have_git_dir())
-		git_dir = get_git_dir();
 	else
 		goto done;
 
@@ -1530,10 +1528,8 @@ static int do_git_config_sequence(const struct config_options *opts,
 	char *user_config = expand_user_path("~/.gitconfig", 0);
 	char *repo_config;
 
-	if (opts->git_dir)
-		repo_config = mkpathdup("%s/config", opts->git_dir);
-	else if (have_git_dir())
-		repo_config = git_pathdup("config");
+	if (opts->commondir)
+		repo_config = mkpathdup("%s/config", opts->commondir);
 	else
 		repo_config = NULL;
 
@@ -1597,6 +1593,11 @@ static void git_config_raw(config_fn_t fn, void *data)
 	struct config_options opts = {0};
 
 	opts.respect_includes = 1;
+	if (have_git_dir()) {
+		opts.commondir = get_git_common_dir();
+		opts.git_dir = get_git_dir();
+	}
+
 	if (git_config_with_options(fn, data, NULL, &opts) < 0)
 		/*
 		 * git_config_with_options() normally returns only
@@ -1638,11 +1639,13 @@ 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;
 
-	if (have_git_dir())
+	if (have_git_dir()) {
+		opts.commondir = get_git_common_dir();
 		opts.git_dir = get_git_dir();
 	/*
 	 * When setup_git_directory() was not yet asked to discover the
@@ -1652,12 +1655,15 @@ 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.commondir = commondir.buf;
+		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/environment.c b/environment.c
index 1f0bda5..aa478e7 100644
--- a/environment.c
+++ b/environment.c
@@ -217,6 +217,8 @@ const char *get_git_dir(void)
 
 const char *get_git_common_dir(void)
 {
+	if (!git_dir)
+		setup_git_env();
 	return git_common_dir;
 }
 
diff --git a/setup.c b/setup.c
index 2435186..beb335c 100644
--- a/setup.c
+++ b/setup.c
@@ -945,19 +945,21 @@ static enum discovery_result setup_git_directory_gently_1(struct strbuf *dir,
 	}
 }
 
-const char *discover_git_directory(struct strbuf *gitdir)
+int 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))
-		return NULL;
+		return -1;
 
 	cwd_len = dir.len;
 	if (setup_git_directory_gently_1(&dir, gitdir, 0) <= 0) {
 		strbuf_release(&dir);
-		return NULL;
+		return -1;
 	}
 
 	/*
@@ -973,8 +975,10 @@ 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);
 
@@ -982,11 +986,12 @@ 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);
 		strbuf_setlen(gitdir, gitdir_offset);
-		return NULL;
+		return -1;
 	}
 
-	return gitdir->buf + gitdir_offset;
+	return 0;
 }
 
 const char *setup_git_directory_gently(int *nongit_ok)