Merge branch 'ao/submodule-wo-gitmodules-checked-out'

The submodule support has been updated to read from the blob at
HEAD:.gitmodules when the .gitmodules file is missing from the
working tree.

* ao/submodule-wo-gitmodules-checked-out:
  t/helper: add test-submodule-nested-repo-config
  submodule: support reading .gitmodules when it's not in the working tree
  submodule: add a helper to check if it is safe to write to .gitmodules
  t7506: clean up .gitmodules properly before setting up new scenario
  submodule: use the 'submodule--helper config' command
  submodule--helper: add a new 'config' subcommand
  t7411: be nicer to future tests and really clean things up
  t7411: merge tests 5 and 6
  submodule: factor out a config_set_in_gitmodules_file_gently function
  submodule: add a print_config_from_gitmodules() helper

16 files changed, 454 insertions, 32 deletions

diff --git a/Makefile b/Makefile
index f77bf17..016fdcd 100644
--- a/Makefile
+++ b/Makefile
@@ -751,6 +751,7 @@ TEST_BUILTINS_OBJS += test-sigchain.o
 TEST_BUILTINS_OBJS += test-strcmp-offset.o
 TEST_BUILTINS_OBJS += test-string-list.o
 TEST_BUILTINS_OBJS += test-submodule-config.o
+TEST_BUILTINS_OBJS += test-submodule-nested-repo-config.o
 TEST_BUILTINS_OBJS += test-subprocess.o
 TEST_BUILTINS_OBJS += test-urlmatch-normalization.o
 TEST_BUILTINS_OBJS += test-wildmatch.o
diff --git a/builtin/grep.c b/builtin/grep.c
index d8508dd..56e4a11 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -422,11 +422,23 @@ static int grep_submodule(struct grep_opt *opt, struct repository *superproject,
 	struct repository submodule;
 	int hit;
 
-	if (!is_submodule_active(superproject, path))
+	/*
+	 * NEEDSWORK: submodules functions need to be protected because they
+	 * access the object store via config_from_gitmodules(): the latter
+	 * uses get_oid() which, for now, relies on the global the_repository
+	 * object.
+	 */
+	grep_read_lock();
+
+	if (!is_submodule_active(superproject, path)) {
+		grep_read_unlock();
 		return 0;
+	}
 
-	if (repo_submodule_init(&submodule, superproject, path))
+	if (repo_submodule_init(&submodule, superproject, path)) {
+		grep_read_unlock();
 		return 0;
+	}
 
 	repo_read_gitmodules(&submodule);
 
@@ -440,7 +452,6 @@ static int grep_submodule(struct grep_opt *opt, struct repository *superproject,
 	 * store is no longer global and instead is a member of the repository
 	 * object.
 	 */
-	grep_read_lock();
 	add_to_alternates_memory(submodule.objects->objectdir);
 	grep_read_unlock();
 
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 676175b..d38113a 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -2141,6 +2141,45 @@ static int check_name(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static int module_config(int argc, const char **argv, const char *prefix)
+{
+	enum {
+		CHECK_WRITEABLE = 1
+	} command = 0;
+
+	struct option module_config_options[] = {
+		OPT_CMDMODE(0, "check-writeable", &command,
+			    N_("check if it is safe to write to the .gitmodules file"),
+			    CHECK_WRITEABLE),
+		OPT_END()
+	};
+	const char *const git_submodule_helper_usage[] = {
+		N_("git submodule--helper config name [value]"),
+		N_("git submodule--helper config --check-writeable"),
+		NULL
+	};
+
+	argc = parse_options(argc, argv, prefix, module_config_options,
+			     git_submodule_helper_usage, PARSE_OPT_KEEP_ARGV0);
+
+	if (argc == 1 && command == CHECK_WRITEABLE)
+		return is_writing_gitmodules_ok() ? 0 : -1;
+
+	/* Equivalent to ACTION_GET in builtin/config.c */
+	if (argc == 2)
+		return print_config_from_gitmodules(the_repository, argv[1]);
+
+	/* Equivalent to ACTION_SET in builtin/config.c */
+	if (argc == 3) {
+		if (!is_writing_gitmodules_ok())
+			die(_("please make sure that the .gitmodules file is in the working tree"));
+
+		return config_set_in_gitmodules_file_gently(argv[1], argv[2]);
+	}
+
+	usage_with_options(git_submodule_helper_usage, module_config_options);
+}
+
 #define SUPPORT_SUPER_PREFIX (1<<0)
 
 struct cmd_struct {
@@ -2170,6 +2209,7 @@ static struct cmd_struct commands[] = {
 	{"absorb-git-dirs", absorb_git_dirs, SUPPORT_SUPER_PREFIX},
 	{"is-active", is_active, 0},
 	{"check-name", check_name, 0},
+	{"config", module_config, 0},
 };
 
 int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
diff --git a/cache.h b/cache.h
index a59141f..8ac4adb 100644
--- a/cache.h
+++ b/cache.h
@@ -486,6 +486,8 @@ static inline enum object_type object_type(unsigned int mode)
 #define INFOATTRIBUTES_FILE "info/attributes"
 #define ATTRIBUTE_MACRO_PREFIX "[attr]"
 #define GITMODULES_FILE ".gitmodules"
+#define GITMODULES_INDEX ":.gitmodules"
+#define GITMODULES_HEAD "HEAD:.gitmodules"
 #define GIT_NOTES_REF_ENVIRONMENT "GIT_NOTES_REF"
 #define GIT_NOTES_DEFAULT_REF "refs/notes/commits"
 #define GIT_NOTES_DISPLAY_REF_ENVIRONMENT "GIT_NOTES_DISPLAY_REF"
diff --git a/git-submodule.sh b/git-submodule.sh
index c09eb3e..5e608f8 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -72,7 +72,7 @@ get_submodule_config () {
 	value=$(git config submodule."$name"."$option")
 	if test -z "$value"
 	then
-		value=$(git config -f .gitmodules submodule."$name"."$option")
+		value=$(git submodule--helper config submodule."$name"."$option")
 	fi
 	printf '%s' "${value:-$default}"
 }
@@ -164,6 +164,11 @@ cmd_add()
 		shift
 	done
 
+	if ! git submodule--helper config --check-writeable >/dev/null 2>&1
+	then
+		 die "$(eval_gettext "please make sure that the .gitmodules file is in the working tree")"
+	fi
+
 	if test -n "$reference_path"
 	then
 		is_absolute_path "$reference_path" ||
@@ -288,11 +293,11 @@ or you are unsure what this means choose another name with the '--name' option."
 	git add --no-warn-embedded-repo $force "$sm_path" ||
 	die "$(eval_gettext "Failed to add submodule '\$sm_path'")"
 
-	git config -f .gitmodules submodule."$sm_name".path "$sm_path" &&
-	git config -f .gitmodules submodule."$sm_name".url "$repo" &&
+	git submodule--helper config submodule."$sm_name".path "$sm_path" &&
+	git submodule--helper config submodule."$sm_name".url "$repo" &&
 	if test -n "$branch"
 	then
-		git config -f .gitmodules submodule."$sm_name".branch "$branch"
+		git submodule--helper config submodule."$sm_name".branch "$branch"
 	fi &&
 	git add --force .gitmodules ||
 	die "$(eval_gettext "Failed to register submodule '\$sm_path'")"
diff --git a/submodule-config.c b/submodule-config.c
index b132f7a..52702c6 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "dir.h"
 #include "repository.h"
 #include "config.h"
 #include "submodule-config.h"
@@ -613,8 +614,34 @@ static void submodule_cache_check_init(struct repository *repo)
 static void config_from_gitmodules(config_fn_t fn, struct repository *repo, void *data)
 {
 	if (repo->worktree) {
-		char *file = repo_worktree_path(repo, GITMODULES_FILE);
-		git_config_from_file(fn, file, data);
+		struct git_config_source config_source = { 0 };
+		const struct config_options opts = { 0 };
+		struct object_id oid;
+		char *file;
+
+		file = repo_worktree_path(repo, GITMODULES_FILE);
+		if (file_exists(file)) {
+			config_source.file = file;
+		} else if (repo->submodule_prefix) {
+			/*
+			 * When get_oid and config_with_options, used below,
+			 * become able to work on a specific repository, this
+			 * warning branch can be removed.
+			 */
+			warning("nested submodules without %s in the working tree are not supported yet",
+				GITMODULES_FILE);
+			goto out;
+		} else if (get_oid(GITMODULES_INDEX, &oid) >= 0) {
+			config_source.blob = GITMODULES_INDEX;
+		} else if (get_oid(GITMODULES_HEAD, &oid) >= 0) {
+			config_source.blob = GITMODULES_HEAD;
+		} else {
+			goto out;
+		}
+
+		config_with_options(fn, data, &config_source, &opts);
+
+out:
 		free(file);
 	}
 }
@@ -692,6 +719,43 @@ void submodule_free(struct repository *r)
 		submodule_cache_clear(r->submodule_cache);
 }
 
+static int config_print_callback(const char *var, const char *value, void *cb_data)
+{
+	char *wanted_key = cb_data;
+
+	if (!strcmp(wanted_key, var))
+		printf("%s\n", value);
+
+	return 0;
+}
+
+int print_config_from_gitmodules(struct repository *repo, const char *key)
+{
+	int ret;
+	char *store_key;
+
+	ret = git_config_parse_key(key, &store_key, NULL);
+	if (ret < 0)
+		return CONFIG_INVALID_KEY;
+
+	config_from_gitmodules(config_print_callback, repo, store_key);
+
+	free(store_key);
+	return 0;
+}
+
+int config_set_in_gitmodules_file_gently(const char *key, const char *value)
+{
+	int ret;
+
+	ret = git_config_set_in_file_gently(GITMODULES_FILE, key, value);
+	if (ret < 0)
+		/* Maybe the user already did that, don't error out here */
+		warning(_("Could not update .gitmodules entry %s"), key);
+
+	return ret;
+}
+
 struct fetch_config {
 	int *max_children;
 	int *recurse_submodules;
diff --git a/submodule-config.h b/submodule-config.h
index dc7278e..4dc9b07 100644
--- a/submodule-config.h
+++ b/submodule-config.h
@@ -48,6 +48,8 @@ const struct submodule *submodule_from_path(struct repository *r,
 					    const struct object_id *commit_or_tree,
 					    const char *path);
 void submodule_free(struct repository *r);
+int print_config_from_gitmodules(struct repository *repo, const char *key);
+int config_set_in_gitmodules_file_gently(const char *key, const char *value);
 
 /*
  * Returns 0 if the name is syntactically acceptable as a submodule "name"
diff --git a/submodule.c b/submodule.c
index a2701ed..6415cc5 100644
--- a/submodule.c
+++ b/submodule.c
@@ -52,6 +52,24 @@ int is_gitmodules_unmerged(const struct index_state *istate)
 }
 
 /*
+ * Check if the .gitmodules file is safe to write.
+ *
+ * Writing to the .gitmodules file requires that the file exists in the
+ * working tree or, if it doesn't, that a brand new .gitmodules file is going
+ * to be created (i.e. it's neither in the index nor in the current branch).
+ *
+ * It is not safe to write to .gitmodules if it's not in the working tree but
+ * it is in the index or in the current branch, because writing new values
+ * (and staging them) would blindly overwrite ALL the old content.
+ */
+int is_writing_gitmodules_ok(void)
+{
+	struct object_id oid;
+	return file_exists(GITMODULES_FILE) ||
+		(get_oid(GITMODULES_INDEX, &oid) < 0 && get_oid(GITMODULES_HEAD, &oid) < 0);
+}
+
+/*
  * Check if the .gitmodules file has unstaged modifications.  This must be
  * checked before allowing modifications to the .gitmodules file with the
  * intention to stage them later, because when continuing we would stage the
@@ -89,6 +107,7 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 {
 	struct strbuf entry = STRBUF_INIT;
 	const struct submodule *submodule;
+	int ret;
 
 	if (!file_exists(GITMODULES_FILE)) /* Do nothing without .gitmodules */
 		return -1;
@@ -104,14 +123,9 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 	strbuf_addstr(&entry, "submodule.");
 	strbuf_addstr(&entry, submodule->name);
 	strbuf_addstr(&entry, ".path");
-	if (git_config_set_in_file_gently(GITMODULES_FILE, entry.buf, newpath) < 0) {
-		/* Maybe the user already did that, don't error out here */
-		warning(_("Could not update .gitmodules entry %s"), entry.buf);
-		strbuf_release(&entry);
-		return -1;
-	}
+	ret = config_set_in_gitmodules_file_gently(entry.buf, newpath);
 	strbuf_release(&entry);
-	return 0;
+	return ret;
 }
 
 /*
diff --git a/submodule.h b/submodule.h
index a8a4fe8..a680214 100644
--- a/submodule.h
+++ b/submodule.h
@@ -40,6 +40,7 @@ struct submodule_update_strategy {
 #define SUBMODULE_UPDATE_STRATEGY_INIT {SM_UPDATE_UNSPECIFIED, NULL}
 
 int is_gitmodules_unmerged(const struct index_state *istate);
+int is_writing_gitmodules_ok(void);
 int is_staging_gitmodules_ok(struct index_state *istate);
 int update_path_in_gitmodules(const char *oldpath, const char *newpath);
 int remove_path_from_gitmodules(const char *path);
diff --git a/t/helper/test-submodule-nested-repo-config.c b/t/helper/test-submodule-nested-repo-config.c
new file mode 100644
index 0000000..a31e2a9
--- /dev/null
+++ b/t/helper/test-submodule-nested-repo-config.c
@@ -0,0 +1,30 @@
+#include "test-tool.h"
+#include "submodule-config.h"
+
+static void die_usage(int argc, const char **argv, const char *msg)
+{
+	fprintf(stderr, "%s\n", msg);
+	fprintf(stderr, "Usage: %s <submodulepath> <config name>\n", argv[0]);
+	exit(1);
+}
+
+int cmd__submodule_nested_repo_config(int argc, const char **argv)
+{
+	struct repository submodule;
+
+	if (argc < 3)
+		die_usage(argc, argv, "Wrong number of arguments.");
+
+	setup_git_directory();
+
+	if (repo_submodule_init(&submodule, the_repository, argv[1])) {
+		die_usage(argc, argv, "Submodule not found.");
+	}
+
+	/* Read the config of _child_ submodules. */
+	print_config_from_gitmodules(&submodule, argv[2]);
+
+	submodule_free(the_repository);
+
+	return 0;
+}
diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c
index 5df8b68..bfb195b 100644
--- a/t/helper/test-tool.c
+++ b/t/helper/test-tool.c
@@ -46,6 +46,7 @@ static struct test_cmd cmds[] = {
 	{ "strcmp-offset", cmd__strcmp_offset },
 	{ "string-list", cmd__string_list },
 	{ "submodule-config", cmd__submodule_config },
+	{ "submodule-nested-repo-config", cmd__submodule_nested_repo_config },
 	{ "subprocess", cmd__subprocess },
 	{ "urlmatch-normalization", cmd__urlmatch_normalization },
 	{ "wildmatch", cmd__wildmatch },
diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h
index 71f470b..042f124 100644
--- a/t/helper/test-tool.h
+++ b/t/helper/test-tool.h
@@ -42,6 +42,7 @@ int cmd__sigchain(int argc, const char **argv);
 int cmd__strcmp_offset(int argc, const char **argv);
 int cmd__string_list(int argc, const char **argv);
 int cmd__submodule_config(int argc, const char **argv);
+int cmd__submodule_nested_repo_config(int argc, const char **argv);
 int cmd__subprocess(int argc, const char **argv);
 int cmd__urlmatch_normalization(int argc, const char **argv);
 int cmd__wildmatch(int argc, const char **argv);
diff --git a/t/t7411-submodule-config.sh b/t/t7411-submodule-config.sh
index 0bde585..89690b7 100755
--- a/t/t7411-submodule-config.sh
+++ b/t/t7411-submodule-config.sh
@@ -82,29 +82,23 @@ Submodule name: 'a' for path 'b'
 Submodule name: 'submodule' for path 'submodule'
 EOF
 
-test_expect_success 'error in one submodule config lets continue' '
+test_expect_success 'error in history of one submodule config lets continue, stderr message contains blob ref' '
+	ORIG=$(git -C super rev-parse HEAD) &&
+	test_when_finished "git -C super reset --hard $ORIG" &&
 	(cd super &&
 		cp .gitmodules .gitmodules.bak &&
 		echo "	value = \"" >>.gitmodules &&
 		git add .gitmodules &&
 		mv .gitmodules.bak .gitmodules &&
 		git commit -m "add error" &&
-		test-tool submodule-config \
-			HEAD b \
-			HEAD submodule \
-				>actual &&
-		test_cmp expect_error actual
-	)
-'
-
-test_expect_success 'error message contains blob reference' '
-	(cd super &&
 		sha1=$(git rev-parse HEAD) &&
 		test-tool submodule-config \
 			HEAD b \
 			HEAD submodule \
-				2>actual_err &&
-		test_i18ngrep "submodule-blob $sha1:.gitmodules" actual_err >/dev/null
+				>actual \
+				2>actual_stderr &&
+		test_cmp expect_error actual &&
+		test_i18ngrep "submodule-blob $sha1:.gitmodules" actual_stderr >/dev/null
 	)
 '
 
@@ -123,6 +117,8 @@ test_expect_success 'using different treeishs works' '
 '
 
 test_expect_success 'error in history in fetchrecursesubmodule lets continue' '
+	ORIG=$(git -C super rev-parse HEAD) &&
+	test_when_finished "git -C super reset --hard $ORIG" &&
 	(cd super &&
 		git config -f .gitmodules \
 			submodule.submodule.fetchrecursesubmodules blabla &&
@@ -134,8 +130,123 @@ test_expect_success 'error in history in fetchrecursesubmodule lets continue' '
 			HEAD b \
 			HEAD submodule \
 				>actual &&
-		test_cmp expect_error actual  &&
-		git reset --hard HEAD^
+		test_cmp expect_error actual
+	)
+'
+
+test_expect_success 'reading submodules config from the working tree with "submodule--helper config"' '
+	(cd super &&
+		echo "../submodule" >expect &&
+		git submodule--helper config submodule.submodule.url >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'writing submodules config with "submodule--helper config"' '
+	(cd super &&
+		echo "new_url" >expect &&
+		git submodule--helper config submodule.submodule.url "new_url" &&
+		git submodule--helper config submodule.submodule.url >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'overwriting unstaged submodules config with "submodule--helper config"' '
+	test_when_finished "git -C super checkout .gitmodules" &&
+	(cd super &&
+		echo "newer_url" >expect &&
+		git submodule--helper config submodule.submodule.url "newer_url" &&
+		git submodule--helper config submodule.submodule.url >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'writeable .gitmodules when it is in the working tree' '
+	git -C super submodule--helper config --check-writeable
+'
+
+test_expect_success 'writeable .gitmodules when it is nowhere in the repository' '
+	ORIG=$(git -C super rev-parse HEAD) &&
+	test_when_finished "git -C super reset --hard $ORIG" &&
+	(cd super &&
+		git rm .gitmodules &&
+		git commit -m "remove .gitmodules from the current branch" &&
+		git submodule--helper config --check-writeable
+	)
+'
+
+test_expect_success 'non-writeable .gitmodules when it is in the index but not in the working tree' '
+	test_when_finished "git -C super checkout .gitmodules" &&
+	(cd super &&
+		rm -f .gitmodules &&
+		test_must_fail git submodule--helper config --check-writeable
+	)
+'
+
+test_expect_success 'non-writeable .gitmodules when it is in the current branch but not in the index' '
+	ORIG=$(git -C super rev-parse HEAD) &&
+	test_when_finished "git -C super reset --hard $ORIG" &&
+	(cd super &&
+		git rm .gitmodules &&
+		test_must_fail git submodule--helper config --check-writeable
+	)
+'
+
+test_expect_success 'reading submodules config from the index when .gitmodules is not in the working tree' '
+	ORIG=$(git -C super rev-parse HEAD) &&
+	test_when_finished "git -C super reset --hard $ORIG" &&
+	(cd super &&
+		git submodule--helper config submodule.submodule.url "staged_url" &&
+		git add .gitmodules &&
+		rm -f .gitmodules &&
+		echo "staged_url" >expect &&
+		git submodule--helper config submodule.submodule.url >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'reading submodules config from the current branch when .gitmodules is not in the index' '
+	ORIG=$(git -C super rev-parse HEAD) &&
+	test_when_finished "git -C super reset --hard $ORIG" &&
+	(cd super &&
+		git rm .gitmodules &&
+		echo "../submodule" >expect &&
+		git submodule--helper config submodule.submodule.url >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'reading nested submodules config' '
+	(cd super &&
+		git init submodule/nested_submodule &&
+		echo "a" >submodule/nested_submodule/a &&
+		git -C submodule/nested_submodule add a &&
+		git -C submodule/nested_submodule commit -m "add a" &&
+		git -C submodule submodule add ./nested_submodule &&
+		git -C submodule add nested_submodule &&
+		git -C submodule commit -m "added nested_submodule" &&
+		git add submodule &&
+		git commit -m "updated submodule" &&
+		echo "./nested_submodule" >expect &&
+		test-tool submodule-nested-repo-config \
+			submodule submodule.nested_submodule.url >actual &&
+		test_cmp expect actual
+	)
+'
+
+# When this test eventually passes, before turning it into
+# test_expect_success, remember to replace the test_i18ngrep below with
+# a "test_must_be_empty warning" to be sure that the warning is actually
+# removed from the code.
+test_expect_failure 'reading nested submodules config when .gitmodules is not in the working tree' '
+	test_when_finished "git -C super/submodule checkout .gitmodules" &&
+	(cd super &&
+		echo "./nested_submodule" >expect &&
+		rm submodule/.gitmodules &&
+		test-tool submodule-nested-repo-config \
+			submodule submodule.nested_submodule.url >actual 2>warning &&
+		test_i18ngrep "nested submodules without %s in the working tree are not supported yet" warning &&
+		test_cmp expect actual
 	)
 '
 
diff --git a/t/t7418-submodule-sparse-gitmodules.sh b/t/t7418-submodule-sparse-gitmodules.sh
new file mode 100755
index 0000000..3f7f2718
--- /dev/null
+++ b/t/t7418-submodule-sparse-gitmodules.sh
@@ -0,0 +1,122 @@
+#!/bin/sh
+#
+# Copyright (C) 2018  Antonio Ospite <ao2@ao2.it>
+#
+
+test_description='Test reading/writing .gitmodules when not in the working tree
+
+This test verifies that, when .gitmodules is in the current branch but is not
+in the working tree reading from it still works but writing to it does not.
+
+The test setup uses a sparse checkout, however the same scenario can be set up
+also by committing .gitmodules and then just removing it from the filesystem.
+'
+
+. ./test-lib.sh
+
+test_expect_success 'sparse checkout setup which hides .gitmodules' '
+	git init upstream &&
+	git init submodule &&
+	(cd submodule &&
+		echo file >file &&
+		git add file &&
+		test_tick &&
+		git commit -m "Add file"
+	) &&
+	(cd upstream &&
+		git submodule add ../submodule &&
+		test_tick &&
+		git commit -m "Add submodule"
+	) &&
+	git clone upstream super &&
+	(cd super &&
+		cat >.git/info/sparse-checkout <<-\EOF &&
+		/*
+		!/.gitmodules
+		EOF
+		git config core.sparsecheckout true &&
+		git read-tree -m -u HEAD &&
+		test_path_is_missing .gitmodules
+	)
+'
+
+test_expect_success 'reading gitmodules config file when it is not checked out' '
+	echo "../submodule" >expect &&
+	git -C super submodule--helper config submodule.submodule.url >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'not writing gitmodules config file when it is not checked out' '
+	test_must_fail git -C super submodule--helper config submodule.submodule.url newurl &&
+	test_path_is_missing super/.gitmodules
+'
+
+test_expect_success 'initialising submodule when the gitmodules config is not checked out' '
+	test_must_fail git -C super config submodule.submodule.url &&
+	git -C super submodule init &&
+	git -C super config submodule.submodule.url >actual &&
+	echo "$(pwd)/submodule" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'updating submodule when the gitmodules config is not checked out' '
+	test_path_is_missing super/submodule/file &&
+	git -C super submodule update &&
+	test_cmp submodule/file super/submodule/file
+'
+
+ORIG_SUBMODULE=$(git -C submodule rev-parse HEAD)
+ORIG_UPSTREAM=$(git -C upstream rev-parse HEAD)
+ORIG_SUPER=$(git -C super rev-parse HEAD)
+
+test_expect_success 're-updating submodule when the gitmodules config is not checked out' '
+	test_when_finished "git -C submodule reset --hard $ORIG_SUBMODULE;
+			    git -C upstream reset --hard $ORIG_UPSTREAM;
+			    git -C super reset --hard $ORIG_SUPER;
+			    git -C upstream submodule update --remote;
+			    git -C super pull;
+			    git -C super submodule update --remote" &&
+	(cd submodule &&
+		echo file2 >file2 &&
+		git add file2 &&
+		test_tick &&
+		git commit -m "Add file2 to submodule"
+	) &&
+	(cd upstream &&
+		git submodule update --remote &&
+		git add submodule &&
+		test_tick &&
+		git commit -m "Update submodule"
+	) &&
+	git -C super pull &&
+	# The --for-status options reads the gitmodules config
+	git -C super submodule summary --for-status >actual &&
+	rev1=$(git -C submodule rev-parse --short HEAD) &&
+	rev2=$(git -C submodule rev-parse --short HEAD^) &&
+	cat >expect <<-EOF &&
+	* submodule ${rev1}...${rev2} (1):
+	  < Add file2 to submodule
+
+	EOF
+	test_cmp expect actual &&
+	# Test that the update actually succeeds
+	test_path_is_missing super/submodule/file2 &&
+	git -C super submodule update &&
+	test_cmp submodule/file2 super/submodule/file2 &&
+	git -C super status --short >output &&
+	test_must_be_empty output
+'
+
+test_expect_success 'not adding submodules when the gitmodules config is not checked out' '
+	git clone submodule new_submodule &&
+	test_must_fail git -C super submodule add ../new_submodule &&
+	test_path_is_missing .gitmodules
+'
+
+# This test checks that the previous "git submodule add" did not leave the
+# repository in a spurious state when it failed.
+test_expect_success 'init submodule still works even after the previous add failed' '
+	git -C super submodule init
+'
+
+test_done
diff --git a/t/t7506-status-submodule.sh b/t/t7506-status-submodule.sh
index 943708f..08629a6 100755
--- a/t/t7506-status-submodule.sh
+++ b/t/t7506-status-submodule.sh
@@ -325,7 +325,8 @@ test_expect_success 'setup superproject with untracked file in nested submodule'
 	(
 		cd super &&
 		git clean -dfx &&
-		rm .gitmodules &&
+		git rm .gitmodules &&
+		git commit -m "remove .gitmodules" &&
 		git submodule add -f ./sub1 &&
 		git submodule add -f ./sub2 &&
 		git submodule add -f ./sub1 sub3 &&
diff --git a/t/t7814-grep-recurse-submodules.sh b/t/t7814-grep-recurse-submodules.sh
index 7184113..fa475d5 100755
--- a/t/t7814-grep-recurse-submodules.sh
+++ b/t/t7814-grep-recurse-submodules.sh
@@ -380,4 +380,20 @@ test_expect_success 'grep --recurse-submodules should pass the pattern type alon
 	fi
 '
 
+# Recursing down into nested submodules which do not have .gitmodules in their
+# working tree does not work yet. This is because config_from_gitmodules()
+# uses get_oid() and the latter is still not able to get objects from an
+# arbitrary repository (the nested submodule, in this case).
+test_expect_failure 'grep --recurse-submodules with submodules without .gitmodules in the working tree' '
+	test_when_finished "git -C submodule checkout .gitmodules" &&
+	rm submodule/.gitmodules &&
+	git grep --recurse-submodules -e "(.|.)[\d]" >actual &&
+	cat >expect <<-\EOF &&
+	a:(1|2)d(3|4)
+	submodule/a:(1|2)d(3|4)
+	submodule/sub/a:(1|2)d(3|4)
+	EOF
+	test_cmp expect actual
+'
+
 test_done