[PATCH 1/2] submodule--helper: set alternateLocation for cloned submodules

[vi0oss@gmail.com]

From: "Vitaly \"_Vi\" Shukela" <vi0oss@gmail.com>

In 31224cbdc7 (clone: recursive and reference option triggers
submodule alternates, 2016-08-17) a mechanism was added to
have submodules referenced.  It did not address _nested_
submodules, however.

This patch makes all not just the root repository, but also
all submodules (recursively) have submodule.alternateLocation
and submodule.alternateErrorStrategy configured, making Git
search for possible alternates for nested submodules as well.

As submodule's alternate target does not end in .git/objects
(rather .git/modules/qqqqqq/objects), this alternate target
path restriction for in add_possible_reference_from_superproject
relates from "*.git/objects" to just */objects".

New tests have been added to t7408-submodule-reference.

Signed-off-by: Vitaly _Vi Shukela <vi0oss@gmail.com>
---

Notes:
    Resolved issues pointed by Stefan Beller except of
    the one about loosened path check, which he aggreed
    to be relaxed for this case.

 builtin/submodule--helper.c    | 21 ++++++++++--
 t/t7408-submodule-reference.sh | 72 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 2 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 4beeda5..7b7633d 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -498,9 +498,9 @@ static int add_possible_reference_from_superproject(
 
 	/*
 	 * If the alternate object store is another repository, try the
-	 * standard layout with .git/modules/<name>/objects
+	 * standard layout with .git/(modules/<name>)+/objects
 	 */
-	if (ends_with(alt->path, ".git/objects")) {
+	if (ends_with(alt->path, "/objects")) {
 		char *sm_alternate;
 		struct strbuf sb = STRBUF_INIT;
 		struct strbuf err = STRBUF_INIT;
@@ -583,6 +583,7 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 	struct strbuf rel_path = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT;
 	struct string_list reference = STRING_LIST_INIT_NODUP;
+	char *sm_alternate = NULL, *error_strategy = NULL;
 
 	struct option module_clone_options[] = {
 		OPT_STRING(0, "prefix", &prefix,
@@ -672,6 +673,22 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 		die(_("could not get submodule directory for '%s'"), path);
 	git_config_set_in_file(p, "core.worktree",
 			       relative_path(path, sm_gitdir, &rel_path));
+
+	/* setup alternateLocation and alternateErrorStrategy in the cloned submodule if needed */
+	git_config_get_string("submodule.alternateLocation", &sm_alternate);
+	if (sm_alternate) {
+		git_config_set_in_file(p, "submodule.alternateLocation",
+					   sm_alternate);
+	}
+	git_config_get_string("submodule.alternateErrorStrategy", &error_strategy);
+	if (error_strategy) {
+		git_config_set_in_file(p, "submodule.alternateErrorStrategy",
+					   error_strategy);
+	}
+
+		free(sm_alternate);
+		free(error_strategy);
+
 	strbuf_release(&sb);
 	strbuf_release(&rel_path);
 	free(sm_gitdir);
diff --git a/t/t7408-submodule-reference.sh b/t/t7408-submodule-reference.sh
index 1c1e289..ef7771b 100755
--- a/t/t7408-submodule-reference.sh
+++ b/t/t7408-submodule-reference.sh
@@ -125,4 +125,76 @@ test_expect_success 'ignoring missing submodule alternates passes clone and subm
 	)
 '
 
+test_expect_success 'preparing second superproject with a nested submodule' '
+	test_create_repo supersuper &&
+	(
+		cd supersuper &&
+		echo "I am super super." >file &&
+		git add file &&
+		git commit -m B-super-super-initial
+		git submodule add "file://$base_dir/super" subwithsub &&
+		git commit -m B-super-super-added &&
+		git submodule update --init --recursive &&
+		git repack -ad
+	)
+'
+
+# At this point there are three root-level positories: A, B, super and super2
+
+test_expect_success 'nested submodule alternate in works and is actually used' '
+	test_when_finished "rm -rf supersuper-clone" &&
+	git clone --recursive --reference supersuper supersuper supersuper-clone &&
+	(
+		cd supersuper-clone &&
+		# test superproject has alternates setup correctly
+		test_alternate_is_used .git/objects/info/alternates . &&
+		# immediate submodule has alternate:
+		test_alternate_is_used .git/modules/subwithsub/objects/info/alternates subwithsub
+		# nested submodule also has alternate:
+		test_alternate_is_used .git/modules/subwithsub/modules/sub/objects/info/alternates subwithsub/sub
+	)
+'
+
+test_expect_success 'missing nested submodule alternate fails clone and submodule update' '
+	test_when_finished "rm -rf supersuper-clone supersuper2" &&
+	git clone supersuper supersuper2 &&
+	(
+		cd supersuper2 &&
+		git submodule update --init
+	) &&
+	test_must_fail git clone --recursive --reference supersuper2 supersuper2 supersuper-clone &&
+	(
+		cd supersuper-clone &&
+		# test superproject has alternates setup correctly
+		test_alternate_is_used .git/objects/info/alternates . &&
+		# update of the submodule fails
+		test_must_fail git submodule update --init --recursive &&
+		# immediate submodule has alternate:
+		test_alternate_is_used .git/modules/subwithsub/objects/info/alternates subwithsub
+		# but nested submodule has no alternate:
+		test_must_fail test_alternate_is_used .git/modules/subwithsub/modules/sub/objects/info/alternates subwithsub/sub
+	)
+'
+
+test_expect_success 'missing nested submodule alternate in --reference-if-able mode' '
+	test_when_finished "rm -rf supersuper-clone supersuper2" &&
+	git clone supersuper supersuper2 &&
+	(
+		cd supersuper2 &&
+		git submodule update --init
+	) &&
+	git clone --recursive --reference-if-able supersuper2 supersuper2 supersuper-clone &&
+	(
+		cd supersuper-clone &&
+		# test superproject has alternates setup correctly
+		test_alternate_is_used .git/objects/info/alternates . &&
+		# update of the submodule fails
+		test_must_fail git submodule update --init --recursive &&
+		# immediate submodule has alternate:
+		test_alternate_is_used .git/modules/subwithsub/objects/info/alternates subwithsub
+		# but nested submodule has no alternate:
+		test_must_fail test_alternate_is_used .git/modules/subwithsub/modules/sub/objects/info/alternates subwithsub/sub
+	)
+'
+
 test_done
-- 
2.10.2