refs: drop `git_default_branch_name()`

The `git_default_branch_name()` function is a thin wrapper around
`repo_default_branch_name()` with two differences:

  - We implicitly rely on `the_repository`.

  - We cache the default branch name.

None of the callsites of `git_default_branch_name()` are hot code paths
though, so the caching of the branch name is not really required.

Refactor the callsites to use `repo_default_branch_name()` instead and
drop `git_default_branch_name()`, thus getting rid of one more case
where we rely on `the_repository`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -1468,6 +1468,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	} else if (remote_head) {
 		our_head_points_at = NULL;
 	} else {
+		char *to_free = NULL;
 		const char *branch;
 
 		if (!mapped_refs) {
@@ -1480,7 +1481,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 				"refs/heads/", &branch)) {
 			unborn_head  = xstrdup(transport_ls_refs_options.unborn_head_target);
 		} else {
-			branch = git_default_branch_name(0);
+			branch = to_free = repo_default_branch_name(the_repository, 0);
 			unborn_head = xstrfmt("refs/heads/%s", branch);
 		}
 
@@ -1496,6 +1497,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		 * a match.
 		 */
 		our_head_points_at = find_remote_branch(mapped_refs, branch);
+
+		free(to_free);
 	}
 
 	write_refspec_config(src_ref_prefix, our_head_points_at,

builtin/var.c

@@ -46,7 +46,7 @@ static char *pager(int ident_flag UNUSED)
 
 static char *default_branch(int ident_flag UNUSED)
 {
-	return xstrdup_or_null(git_default_branch_name(1));
+	return repo_default_branch_name(the_repository, 1);
 }
 
 static char *shell_path(int ident_flag UNUSED)

refs.c

@@ -664,16 +664,6 @@ char *repo_default_branch_name(struct repository *r, int quiet)
 	return ret;
 }
 
-const char *git_default_branch_name(int quiet)
-{
-	static char *ret;
-
-	if (!ret)
-		ret = repo_default_branch_name(the_repository, quiet);
-
-	return ret;
-}
-
 /*
  * *string and *len will only be substituted, and *string returned (for
  * later free()ing) if the string passed in is a magic short-hand form

refs.h

@@ -169,10 +169,8 @@ int dwim_log(const char *str, int len, struct object_id *oid, char **ref);
 /*
  * Retrieves the default branch name for newly-initialized repositories.
  *
- * The return value of `repo_default_branch_name()` is an allocated string. The
+ * The return value is an allocated string.
- * return value of `git_default_branch_name()` is a singleton.
  */
-const char *git_default_branch_name(int quiet);
 char *repo_default_branch_name(struct repository *r, int quiet);
 
 /*

remote.c

@@ -305,7 +305,7 @@ static void read_remotes_file(struct remote_state *remote_state,
 static void read_branches_file(struct remote_state *remote_state,
 			       struct remote *remote)
 {
-	char *frag;
+	char *frag, *to_free = NULL;
 	struct strbuf buf = STRBUF_INIT;
 	FILE *f = fopen_or_warn(git_path("branches/%s", remote->name), "r");
 
@@ -333,7 +333,7 @@ static void read_branches_file(struct remote_state *remote_state,
 	if (frag)
 		*(frag++) = '\0';
 	else
-		frag = (char *)git_default_branch_name(0);
+		frag = to_free = repo_default_branch_name(the_repository, 0);
 
 	add_url_alias(remote_state, remote, strbuf_detach(&buf, NULL));
 	refspec_appendf(&remote->fetch, "refs/heads/%s:refs/heads/%s",
@@ -345,6 +345,8 @@ static void read_branches_file(struct remote_state *remote_state,
 	 */
 	refspec_appendf(&remote->push, "HEAD:refs/heads/%s", frag);
 	remote->fetch_tags = 1; /* always auto-follow */
+
+	free(to_free);
 }
 
 static int handle_config(const char *key, const char *value,
@@ -2388,11 +2390,13 @@ struct ref *guess_remote_head(const struct ref *head,
 
 	/* If a remote branch exists with the default branch name, let's use it. */
 	if (!all) {
-		char *ref = xstrfmt("refs/heads/%s",
+		char *default_branch = repo_default_branch_name(the_repository, 0);
-				    git_default_branch_name(0));
+		char *ref = xstrfmt("refs/heads/%s", default_branch);
 
 		r = find_ref_by_name(refs, ref);
 		free(ref);
+		free(default_branch);
+
 		if (r && oideq(&r->old_oid, &head->old_oid))
 			return copy_ref(r);
 

setup.c

@@ -2046,6 +2046,7 @@ void create_reference_database(unsigned int ref_storage_format,
 			       const char *initial_branch, int quiet)
 {
 	struct strbuf err = STRBUF_INIT;
+	char *to_free = NULL;
 	int reinit = is_reinit();
 
 	repo_set_ref_storage_format(the_repository, ref_storage_format);
@@ -2060,7 +2061,8 @@ void create_reference_database(unsigned int ref_storage_format,
 		char *ref;
 
 		if (!initial_branch)
-			initial_branch = git_default_branch_name(quiet);
+			initial_branch = to_free =
+				repo_default_branch_name(the_repository, quiet);
 
 		ref = xstrfmt("refs/heads/%s", initial_branch);
 		if (check_refname_format(ref, 0) < 0)
@@ -2077,6 +2079,7 @@ void create_reference_database(unsigned int ref_storage_format,
 			initial_branch);
 
 	strbuf_release(&err);
+	free(to_free);
 }
 
 static int create_default_files(const char *template_path,