Merge branch 'bw/submodule-is-active'

"what URL do we want to update this submodule?" and "are we
interested in this submodule?" are split into two distinct
concepts, and then the way used to express the latter got extended,
paving a way to make it easier to manage a project with many
submodules and make it possible to later extend use of multiple
worktrees for a project with submodules.

* bw/submodule-is-active:
  submodule add: respect submodule.active and submodule.<name>.active
  submodule--helper init: set submodule.<name>.active
  clone: teach --recurse-submodules to optionally take a pathspec
  submodule init: initialize active submodules
  submodule: decouple url and submodule interest
  submodule--helper clone: check for configured submodules using helper
  submodule sync: use submodule--helper is-active
  submodule sync: skip work for inactive submodules
  submodule status: use submodule--helper is-active
  submodule--helper: add is-active subcommand

builtin/submodule--helper.c

@@ -270,6 +270,29 @@ static int module_list_compute(int argc, const char **argv,
 	return result;
 }
 
+static void module_list_active(struct module_list *list)
+{
+	int i;
+	struct module_list active_modules = MODULE_LIST_INIT;
+
+	gitmodules_config();
+
+	for (i = 0; i < list->nr; i++) {
+		const struct cache_entry *ce = list->entries[i];
+
+		if (!is_submodule_initialized(ce->name))
+			continue;
+
+		ALLOC_GROW(active_modules.entries,
+			   active_modules.nr + 1,
+			   active_modules.alloc);
+		active_modules.entries[active_modules.nr++] = ce;
+	}
+
+	free(list->entries);
+	*list = active_modules;
+}
+
 static int module_list(int argc, const char **argv, const char *prefix)
 {
 	int i;
@@ -333,6 +356,18 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
 		die(_("No url found for submodule path '%s' in .gitmodules"),
 			displaypath);
 
+	/*
+	 * NEEDSWORK: In a multi-working-tree world, this needs to be
+	 * set in the per-worktree config.
+	 *
+	 * Set active flag for the submodule being initialized
+	 */
+	if (!is_submodule_initialized(path)) {
+		strbuf_reset(&sb);
+		strbuf_addf(&sb, "submodule.%s.active", sub->name);
+		git_config_set_gently(sb.buf, "true");
+	}
+
 	/*
 	 * Copy url setting when it is not set yet.
 	 * To look up the url in .git/config, we must not fall back to
@@ -420,6 +455,13 @@ static int module_init(int argc, const char **argv, const char *prefix)
 	if (module_list_compute(argc, argv, prefix, &pathspec, &list) < 0)
 		return 1;
 
+	/*
+	 * If there are no path args and submodule.active is set then,
+	 * by default, only initialize 'active' modules.
+	 */
+	if (!argc && git_config_get_value_multi("submodule.active"))
+		module_list_active(&list);
+
 	for (i = 0; i < list.nr; i++)
 		init_submodule(list.entries[i]->name, prefix, quiet);
 
@@ -741,7 +783,6 @@ static int prepare_to_clone_next_submodule(const struct cache_entry *ce,
 	struct strbuf displaypath_sb = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT;
 	const char *displaypath = NULL;
-	char *url = NULL;
 	int needs_cloning = 0;
 
 	if (ce_stage(ce)) {
@@ -775,15 +816,8 @@ static int prepare_to_clone_next_submodule(const struct cache_entry *ce,
 		goto cleanup;
 	}
 
-	/*
-	 * Looking up the url in .git/config.
-	 * We must not fall back to .gitmodules as we only want
-	 * to process configured submodules.
-	 */
-	strbuf_reset(&sb);
-	strbuf_addf(&sb, "submodule.%s.url", sub->name);
-	git_config_get_string(sb.buf, &url);
-	if (!url) {
+	/* Check if the submodule has been initialized. */
+	if (!is_submodule_initialized(ce->name)) {
 		next_submodule_warn_missing(suc, out, displaypath);
 		goto cleanup;
 	}
@@ -817,7 +851,7 @@ static int prepare_to_clone_next_submodule(const struct cache_entry *ce,
 		argv_array_push(&child->args, "--depth=1");
 	argv_array_pushl(&child->args, "--path", sub->path, NULL);
 	argv_array_pushl(&child->args, "--name", sub->name, NULL);
-	argv_array_pushl(&child->args, "--url", url, NULL);
+	argv_array_pushl(&child->args, "--url", sub->url, NULL);
 	if (suc->references.nr) {
 		struct string_list_item *item;
 		for_each_string_list_item(item, &suc->references)
@@ -827,7 +861,6 @@ static int prepare_to_clone_next_submodule(const struct cache_entry *ce,
 		argv_array_push(&child->args, suc->depth);
 
 cleanup:
-	free(url);
 	strbuf_reset(&displaypath_sb);
 	strbuf_reset(&sb);
 
@@ -1109,6 +1142,16 @@ static int absorb_git_dirs(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static int is_active(int argc, const char **argv, const char *prefix)
+{
+	if (argc != 2)
+		die("submodule--helper is-active takes exactly 1 arguments");
+
+	gitmodules_config();
+
+	return !is_submodule_initialized(argv[1]);
+}
+
 #define SUPPORT_SUPER_PREFIX (1<<0)
 
 struct cmd_struct {
@@ -1128,6 +1171,7 @@ static struct cmd_struct commands[] = {
 	{"init", module_init, SUPPORT_SUPER_PREFIX},
 	{"remote-branch", resolve_remote_submodule_branch, 0},
 	{"absorb-git-dirs", absorb_git_dirs, SUPPORT_SUPER_PREFIX},
+	{"is-active", is_active, 0},
 };
 
 int cmd_submodule__helper(int argc, const char **argv, const char *prefix)