Merge branch 'sb/submodule-clone-rr'

"git clone --resurse-submodules --reference $path $URL" is a way to
reduce network transfer cost by borrowing objects in an existing
$path repository when cloning the superproject from $URL; it
learned to also peek into $path for presense of corresponding
repositories of submodules and borrow objects from there when able.

* sb/submodule-clone-rr:
  clone: recursive and reference option triggers submodule alternates
  clone: implement optional references
  clone: clarify option_reference as required
  clone: factor out checking for an alternate path
  submodule--helper update-clone: allow multiple references
  submodule--helper module-clone: allow multiple references
  t7408: merge short tests, factor out testing method
  t7408: modernize style

1 files changed, 123 insertions, 13 deletions

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index e79790f0bd..9d79f1994a 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -442,7 +442,7 @@ static int module_name(int argc, const char **argv, const char *prefix)
 }
 
 static int clone_submodule(const char *path, const char *gitdir, const char *url,
-			   const char *depth, const char *reference, int quiet)
+			   const char *depth, struct string_list *reference, int quiet)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
 
@@ -452,8 +452,12 @@ static int clone_submodule(const char *path, const char *gitdir, const char *url
 		argv_array_push(&cp.args, "--quiet");
 	if (depth && *depth)
 		argv_array_pushl(&cp.args, "--depth", depth, NULL);
-	if (reference && *reference)
-		argv_array_pushl(&cp.args, "--reference", reference, NULL);
+	if (reference->nr) {
+		struct string_list_item *item;
+		for_each_string_list_item(item, reference)
+			argv_array_pushl(&cp.args, "--reference",
+					 item->string, NULL);
+	}
 	if (gitdir && *gitdir)
 		argv_array_pushl(&cp.args, "--separate-git-dir", gitdir, NULL);
 
@@ -467,15 +471,114 @@ static int clone_submodule(const char *path, const char *gitdir, const char *url
 	return run_command(&cp);
 }
 
+struct submodule_alternate_setup {
+	const char *submodule_name;
+	enum SUBMODULE_ALTERNATE_ERROR_MODE {
+		SUBMODULE_ALTERNATE_ERROR_DIE,
+		SUBMODULE_ALTERNATE_ERROR_INFO,
+		SUBMODULE_ALTERNATE_ERROR_IGNORE
+	} error_mode;
+	struct string_list *reference;
+};
+#define SUBMODULE_ALTERNATE_SETUP_INIT { NULL, \
+	SUBMODULE_ALTERNATE_ERROR_IGNORE, NULL }
+
+static int add_possible_reference_from_superproject(
+		struct alternate_object_database *alt, void *sas_cb)
+{
+	struct submodule_alternate_setup *sas = sas_cb;
+
+	/* directory name, minus trailing slash */
+	size_t namelen = alt->name - alt->base - 1;
+	struct strbuf name = STRBUF_INIT;
+	strbuf_add(&name, alt->base, namelen);
+
+	/*
+	 * If the alternate object store is another repository, try the
+	 * standard layout with .git/modules/<name>/objects
+	 */
+	if (ends_with(name.buf, ".git/objects")) {
+		char *sm_alternate;
+		struct strbuf sb = STRBUF_INIT;
+		struct strbuf err = STRBUF_INIT;
+		strbuf_add(&sb, name.buf, name.len - strlen("objects"));
+		/*
+		 * We need to end the new path with '/' to mark it as a dir,
+		 * otherwise a submodule name containing '/' will be broken
+		 * as the last part of a missing submodule reference would
+		 * be taken as a file name.
+		 */
+		strbuf_addf(&sb, "modules/%s/", sas->submodule_name);
+
+		sm_alternate = compute_alternate_path(sb.buf, &err);
+		if (sm_alternate) {
+			string_list_append(sas->reference, xstrdup(sb.buf));
+			free(sm_alternate);
+		} else {
+			switch (sas->error_mode) {
+			case SUBMODULE_ALTERNATE_ERROR_DIE:
+				die(_("submodule '%s' cannot add alternate: %s"),
+				    sas->submodule_name, err.buf);
+			case SUBMODULE_ALTERNATE_ERROR_INFO:
+				fprintf(stderr, _("submodule '%s' cannot add alternate: %s"),
+					sas->submodule_name, err.buf);
+			case SUBMODULE_ALTERNATE_ERROR_IGNORE:
+				; /* nothing */
+			}
+		}
+		strbuf_release(&sb);
+	}
+
+	strbuf_release(&name);
+	return 0;
+}
+
+static void prepare_possible_alternates(const char *sm_name,
+		struct string_list *reference)
+{
+	char *sm_alternate = NULL, *error_strategy = NULL;
+	struct submodule_alternate_setup sas = SUBMODULE_ALTERNATE_SETUP_INIT;
+
+	git_config_get_string("submodule.alternateLocation", &sm_alternate);
+	if (!sm_alternate)
+		return;
+
+	git_config_get_string("submodule.alternateErrorStrategy", &error_strategy);
+
+	if (!error_strategy)
+		error_strategy = xstrdup("die");
+
+	sas.submodule_name = sm_name;
+	sas.reference = reference;
+	if (!strcmp(error_strategy, "die"))
+		sas.error_mode = SUBMODULE_ALTERNATE_ERROR_DIE;
+	else if (!strcmp(error_strategy, "info"))
+		sas.error_mode = SUBMODULE_ALTERNATE_ERROR_INFO;
+	else if (!strcmp(error_strategy, "ignore"))
+		sas.error_mode = SUBMODULE_ALTERNATE_ERROR_IGNORE;
+	else
+		die(_("Value '%s' for submodule.alternateErrorStrategy is not recognized"), error_strategy);
+
+	if (!strcmp(sm_alternate, "superproject"))
+		foreach_alt_odb(add_possible_reference_from_superproject, &sas);
+	else if (!strcmp(sm_alternate, "no"))
+		; /* do nothing */
+	else
+		die(_("Value '%s' for submodule.alternateLocation is not recognized"), sm_alternate);
+
+	free(sm_alternate);
+	free(error_strategy);
+}
+
 static int module_clone(int argc, const char **argv, const char *prefix)
 {
-	const char *name = NULL, *url = NULL;
-	const char *reference = NULL, *depth = NULL;
+	const char *name = NULL, *url = NULL, *depth = NULL;
 	int quiet = 0;
 	FILE *submodule_dot_git;
 	char *p, *path = NULL, *sm_gitdir;
 	struct strbuf rel_path = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT;
+	struct string_list reference = STRING_LIST_INIT_NODUP;
 
 	struct option module_clone_options[] = {
 		OPT_STRING(0, "prefix", &prefix,
@@ -490,8 +593,8 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 		OPT_STRING(0, "url", &url,
 			   N_("string"),
 			   N_("url where to clone the submodule from")),
-		OPT_STRING(0, "reference", &reference,
-			   N_("string"),
+		OPT_STRING_LIST(0, "reference", &reference,
+			   N_("repo"),
 			   N_("reference repository")),
 		OPT_STRING(0, "depth", &depth,
 			   N_("string"),
@@ -527,7 +630,10 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 	if (!file_exists(sm_gitdir)) {
 		if (safe_create_leading_directories_const(sm_gitdir) < 0)
 			die(_("could not create directory '%s'"), sm_gitdir);
-		if (clone_submodule(path, sm_gitdir, url, depth, reference, quiet))
+
+		prepare_possible_alternates(name, &reference);
+
+		if (clone_submodule(path, sm_gitdir, url, depth, &reference, quiet))
 			die(_("clone of '%s' into submodule path '%s' failed"),
 			    url, path);
 	} else {
@@ -579,7 +685,7 @@ struct submodule_update_clone {
 	/* configuration parameters which are passed on to the children */
 	int quiet;
 	int recommend_shallow;
-	const char *reference;
+	struct string_list references;
 	const char *depth;
 	const char *recursive_prefix;
 	const char *prefix;
@@ -595,7 +701,8 @@ struct submodule_update_clone {
 	int failed_clones_nr, failed_clones_alloc;
 };
 #define SUBMODULE_UPDATE_CLONE_INIT {0, MODULE_LIST_INIT, 0, \
-	SUBMODULE_UPDATE_STRATEGY_INIT, 0, -1, NULL, NULL, NULL, NULL, \
+	SUBMODULE_UPDATE_STRATEGY_INIT, 0, -1, STRING_LIST_INIT_DUP, \
+	NULL, NULL, NULL, \
 	STRING_LIST_INIT_DUP, 0, NULL, 0, 0}
 
 
@@ -705,8 +812,11 @@ static int prepare_to_clone_next_submodule(const struct cache_entry *ce,
 	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);
-	if (suc->reference)
-		argv_array_push(&child->args, suc->reference);
+	if (suc->references.nr) {
+		struct string_list_item *item;
+		for_each_string_list_item(item, &suc->references)
+			argv_array_pushl(&child->args, "--reference", item->string, NULL);
+	}
 	if (suc->depth)
 		argv_array_push(&child->args, suc->depth);
 
@@ -829,7 +939,7 @@ static int update_clone(int argc, const char **argv, const char *prefix)
 		OPT_STRING(0, "update", &update,
 			   N_("string"),
 			   N_("rebase, merge, checkout or none")),
-		OPT_STRING(0, "reference", &suc.reference, N_("repo"),
+		OPT_STRING_LIST(0, "reference", &suc.references, N_("repo"),
 			   N_("reference repository")),
 		OPT_STRING(0, "depth", &suc.depth, "<depth>",
 			   N_("Create a shallow clone truncated to the "