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

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

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();
 

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)

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"

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'")"

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;

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"

submodule.c

@@ -51,6 +51,24 @@ int is_gitmodules_unmerged(const struct index_state *istate)
 	return 0;
 }
 
+/*
+ * 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
@@ -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;
 }
 
 /*

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);

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;
+}

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 },

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);