[PATCH v6 06/10] submodule--helper: add gitdir migration command

From

Adrian Ratiu <adrian.ratiu@collabora.com>

Date

Dec 13, 2025, 08:08 UTC

Message-ID

<20251213080817.347922-7-adrian.ratiu@collabora.com>

In-Reply-To

<20251213080817.347922-1-adrian.ratiu@collabora.com>

Suggested-by: Junio C Hamano <gitster@pobox.com>
Suggested-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
---
 Documentation/config/extensions.adoc       |  6 ++-
 builtin/submodule--helper.c                | 58 ++++++++++++++++++++++
 t/t7425-submodule-gitdir-path-extension.sh | 34 +++++++++++++
 3 files changed, 96 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
index 929e4e1bf1..63c8727c3b 100644
--- a/Documentation/config/extensions.adoc
+++ b/Documentation/config/extensions.adoc
@@ -80,8 +80,10 @@ submodulePathConfig:::
 	This extension can also be enabled as a global runtime config, with
 	the local repository config having precedence (overwrites it).
 	Existing pre-extension submodules need to be migrated by adding the
-	missing config entries. This is done manually for now, e.g. for each
-	submodule: "git config submodule.<name>.gitdir .git/modules/<name>".
+	missing config entries. This can be done manually, e.g. for each
+	submodule: "git config submodule.<name>.gitdir .git/modules/<name>",
+	or via the "git submodule--helper migrate-gitdir-configs" command
+	which iterates over all submodules and attempts to migrate them.
 
 worktreeConfig:::
 	If enabled, then worktrees will load config settings from the
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 2b5b4f575b..458dc863df 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -1270,6 +1270,63 @@ static int module_gitdir(int argc, const char **argv, const char *prefix UNUSED,
 	return 0;
 }
 
+static int module_migrate(int argc UNUSED, const char **argv UNUSED,
+			  const char *prefix UNUSED, struct repository *repo)
+{
+	struct strbuf module_dir = STRBUF_INIT;
+	DIR *dir;
+	struct dirent *de;
+
+	if (repo_config_set_gently(repo, "core.repositoryformatversion", "1"))
+		die(_("could not set core.repositoryformatversion to 1. "
+		      "Please enable it for migration to work, for example: "
+		      "git config core.repositoryformatversion 1"));
+
+	if (repo_config_set_gently(repo, "extensions.submodulePathConfig", "true"))
+		die(_("could not enable submodulePathConfig extension. It is required "
+		      "for migration to work. Please enable it in the root repo: "
+		      "git config extensions.submodulePathConfig true"));
+
+	repo->repository_format_submodule_path_cfg = 1;
+
+	repo_git_path_append(repo, &module_dir, "modules/");
+
+	dir = opendir(module_dir.buf);
+	if (!dir)
+		die(_("could not open '%s'"), module_dir.buf);
+
+	while ((de = readdir(dir))) {
+		struct strbuf gitdir_path = STRBUF_INIT;
+		char *key;
+		const char *value;
+
+		if (is_dot_or_dotdot(de->d_name))
+			continue;
+
+		strbuf_addf(&gitdir_path, "%s/%s", module_dir.buf, de->d_name);
+		if (!is_git_directory(gitdir_path.buf)) {
+			strbuf_release(&gitdir_path);
+			continue;
+		}
+		strbuf_release(&gitdir_path);
+
+		key = xstrfmt("submodule.%s.gitdir", de->d_name);
+		if (!repo_config_get_string_tmp(repo, key, &value)) {
+			/* Already has a gitdir config, nothing to do. */
+			free(key);
+			continue;
+		}
+		free(key);
+
+		create_default_gitdir_config(de->d_name);
+	}
+
+	closedir(dir);
+	strbuf_release(&module_dir);
+
+	return 0;
+}
+
 struct sync_cb {
 	const char *prefix;
 	const char *super_prefix;
@@ -3654,6 +3711,7 @@ int cmd_submodule__helper(int argc,
 		NULL
 	};
 	struct option options[] = {
+		OPT_SUBCOMMAND("migrate-gitdir-configs", &fn, module_migrate),
 		OPT_SUBCOMMAND("gitdir", &fn, module_gitdir),
 		OPT_SUBCOMMAND("clone", &fn, module_clone),
 		OPT_SUBCOMMAND("add", &fn, module_add),
diff --git a/t/t7425-submodule-gitdir-path-extension.sh b/t/t7425-submodule-gitdir-path-extension.sh
index 2f198bff82..b7f0e8cdf4 100755
--- a/t/t7425-submodule-gitdir-path-extension.sh
+++ b/t/t7425-submodule-gitdir-path-extension.sh
@@ -181,4 +181,38 @@ test_expect_success 'runtime config extensions.submodulePathConfig on existing r
 	)
 '
 
+test_expect_success 'submodule--helper migrates legacy modules' '
+	git init sm-repo-1 &&
+	test_commit -C sm-repo-1 initial-1 &&
+	git init sm-repo-2 &&
+	test_commit -C sm-repo-2 initial-2 &&
+
+	# ensure the global config is disabled so we can actually test migration
+	git config --global extensions.submodulePathConfig false &&
+
+	git init -b main migrate-test &&
+	(
+		cd migrate-test &&
+
+		git submodule add ../sm-repo-1 sub1 &&
+		git submodule add ../sm-repo-2 sub2 &&
+		test_commit add-submodules &&
+
+		# gitdir configs should not exist
+		test_must_fail git config submodule.sub1.gitdir &&
+		test_must_fail git config submodule.sub2.gitdir &&
+
+		git submodule--helper migrate-gitdir-configs &&
+
+		# gitdir configs must exist after migration
+		git config submodule.sub1.gitdir >actual &&
+		echo ".git/modules/sub1" >expect &&
+		test_cmp expect actual &&
+
+		git config submodule.sub2.gitdir >actual &&
+		echo ".git/modules/sub2" >expect &&
+		test_cmp expect actual
+	)
+'
+
 test_done

-- 
2.51.2