clone: allow more than one --reference

Also add a test to expose a long-standing bug that is triggered when
cloning with --reference option from a local repository that has its own
alternates. The alternate object stores specified on the command line
are lost, and only alternates copied from the source repository remain.
The bug will be fixed in the next patch.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -39,13 +39,23 @@ static const char * const builtin_clone_usage[] = {
 
 static int option_no_checkout, option_bare, option_mirror;
 static int option_local, option_no_hardlinks, option_shared, option_recursive;
-static char *option_template, *option_reference, *option_depth;
+static char *option_template, *option_depth;
 static char *option_origin = NULL;
 static char *option_branch = NULL;
 static const char *real_git_dir;
 static char *option_upload_pack = "git-upload-pack";
 static int option_verbosity;
 static int option_progress;
+static struct string_list option_reference;
+
+static int opt_parse_reference(const struct option *opt, const char *arg, int unset)
+{
+	struct string_list *option_reference = opt->value;
+	if (!arg)
+		return -1;
+	string_list_append(option_reference, arg);
+	return 0;
+}
 
 static struct option builtin_clone_options[] = {
 	OPT__VERBOSITY(&option_verbosity),
@@ -71,8 +81,8 @@ static struct option builtin_clone_options[] = {
 		    "initialize submodules in the clone"),
 	OPT_STRING(0, "template", &option_template, "template-directory",
 		   "directory from which templates will be used"),
-	OPT_STRING(0, "reference", &option_reference, "repo",
-		   "reference repository"),
+	OPT_CALLBACK(0 , "reference", &option_reference, "repo",
+		     "reference repository", &opt_parse_reference),
 	OPT_STRING('o', "origin", &option_origin, "branch",
 		   "use <branch> instead of 'origin' to track upstream"),
 	OPT_STRING('b', "branch", &option_branch, "branch",
@@ -197,7 +207,7 @@ static void strip_trailing_slashes(char *dir)
 	*end = '\0';
 }
 
-static void setup_reference(const char *repo)
+static int add_one_reference(struct string_list_item *item, void *cb_data)
 {
 	const char *ref_git;
 	char *ref_git_copy;
@@ -206,13 +216,13 @@ static void setup_reference(const char *repo)
 	struct transport *transport;
 	const struct ref *extra;
 
-	ref_git = real_path(option_reference);
+	ref_git = real_path(item->string);
 
 	if (is_directory(mkpath("%s/.git/objects", ref_git)))
 		ref_git = mkpath("%s/.git", ref_git);
 	else if (!is_directory(mkpath("%s/objects", ref_git)))
 		die(_("reference repository '%s' is not a local directory."),
-		    option_reference);
+		    item->string);
 
 	ref_git_copy = xstrdup(ref_git);
 
@@ -227,6 +237,12 @@ static void setup_reference(const char *repo)
 	transport_disconnect(transport);
 
 	free(ref_git_copy);
+	return 0;
+}
+
+static void setup_reference(void)
+{
+	for_each_string_list(&option_reference, add_one_reference, NULL);
 }
 
 static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest)
@@ -521,8 +537,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	git_config_set(key.buf, repo);
 	strbuf_reset(&key);
 
-	if (option_reference)
-		setup_reference(git_dir);
+	if (option_reference.nr)
+		setup_reference();
 
 	fetch_pattern = value.buf;
 	refspec = parse_fetch_refspec(1, &fetch_pattern);

t/t5601-clone.sh

@@ -207,4 +207,19 @@ test_expect_success 'clone separate gitdir where target already exists' '
 	test_must_fail git clone --separate-git-dir realgitdir src dst
 '
 
+test_expect_failure 'clone --reference from original' '
+	git clone --shared --bare src src-1 &&
+	git clone --bare src src-2 &&
+	git clone --reference=src-2 --bare src-1 target-8 &&
+	grep /src-2/ target-8/objects/info/alternates
+'
+
+test_expect_success 'clone with more than one --reference' '
+	git clone --bare src src-3 &&
+	git clone --bare src src-4 &&
+	git clone --reference=src-3 --reference=src-4 src target-9 &&
+	grep /src-3/ target-9/.git/objects/info/alternates &&
+	grep /src-4/ target-9/.git/objects/info/alternates
+'
+
 test_done