From 2ab05bcd00679a88985937163800d4e89c334f11 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Mon, 31 Aug 2026 12:02:07 +0200
Subject: [PATCH] builtin/clone: refactor handling of "--reference{,-if-able}"

Users can pass "--reference{,-if-able}" to git-clone(1) to instruct it
to set up alternates for the newly created repository. This allows it to
reuse objects from the source repository so that in the best case we
don't have to clone all objects over.

Those options are handled by the confusingly named `setup_reference()`
function -- without the above context, one might rightfully believe that
it was about refs, not about alternates. The function itself is rather
simple: we loop through all provided alternate paths and then, if such
an alternate is valid, we write it to the object database.

In subsequent commits we're about to consolidate the complete setup of
alternates into this function, and furthermore we'll refactor the setup
of the object database to handle doing this for us instead of writing
the alterantes into it one by one.

Prepare for this refactoring by collecting the alternates into a strvec.
Rename the function to `collect_alternates()` to clarify its scope.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/clone.c | 44 ++++++++++++++++++++++++++++----------------
 1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index 8c990ce0cc..8eae3ac7d9 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -154,24 +154,26 @@ static char *get_repo_path(const char *repo, int *is_bundle)
 	return canon;
 }
 
-static int add_one_reference(struct string_list_item *item, void *cb_data)
+struct add_one_alternate_data {
+	struct strvec *alternates;
+	int required;
+};
+
+static int add_one_alternate(struct string_list_item *item, void *cb_data)
 {
+	struct add_one_alternate_data *data = cb_data;
 	struct strbuf err = STRBUF_INIT;
-	int *required = cb_data;
 	char *ref_git = compute_alternate_path(item->string, &err);
 
 	if (!ref_git) {
-		if (*required)
+		if (data->required)
 			die("%s", err.buf);
 		else
 			fprintf(stderr,
 				_("info: Could not add alternate for '%s': %s\n"),
 				item->string, err.buf);
 	} else {
-		struct strbuf sb = STRBUF_INIT;
-		strbuf_addf(&sb, "%s/objects", ref_git);
-		odb_add_to_alternates_file(the_repository->objects, sb.buf);
-		strbuf_release(&sb);
+		strvec_pushf(data->alternates, "%s/objects", ref_git);
 	}
 
 	strbuf_release(&err);
@@ -218,14 +220,20 @@ static void copy_alternates(struct strbuf *src, const char *src_repo)
 	fclose(in);
 }
 
-static void setup_reference(void)
+static void collect_alternates(struct strvec *alternates)
 {
-	int required = 1;
-	for_each_string_list(&option_required_reference,
-			     add_one_reference, &required);
-	required = 0;
-	for_each_string_list(&option_optional_reference,
-			     add_one_reference, &required);
+	if (option_required_reference.nr || option_optional_reference.nr) {
+		struct add_one_alternate_data data = {
+			.alternates = alternates,
+			.required = 1,
+		};
+
+		for_each_string_list(&option_required_reference,
+				     add_one_alternate, &data);
+		data.required = 0;
+		for_each_string_list(&option_optional_reference,
+				     add_one_alternate, &data);
+	}
 }
 
 static void mkdir_if_missing(const char *pathname, mode_t mode)
@@ -999,6 +1007,7 @@ int cmd_clone(int argc,
 			   N_("uri"), N_("a URI for downloading bundles before fetching from origin remote")),
 		OPT_END()
 	};
+	struct strvec alternates = STRVEC_INIT;
 
 	const char * const builtin_clone_usage[] = {
 		N_("git clone [<options>] [--] <repo> [<dir>]"),
@@ -1343,8 +1352,10 @@ int cmd_clone(int argc,
 		warning(_("--local is ignored"));
 
 	create_object_database(the_repository);
-	if (option_required_reference.nr || option_optional_reference.nr)
-		setup_reference();
+	collect_alternates(&alternates);
+
+	for (size_t i = 0; i < alternates.nr; i++)
+		odb_add_to_alternates_file(the_repository->objects, alternates.v[i]);
 
 	transport = transport_get(remote, path ? path : remote->url.v[0]);
 	transport_set_verbosity(transport, option_verbosity, option_progress);
@@ -1641,6 +1652,7 @@ int cmd_clone(int argc,
 	string_list_clear(&option_not, 0);
 	string_list_clear(&option_config, 0);
 	string_list_clear(&server_options, 0);
+	strvec_clear(&alternates);
 
 	free(remote_name);
 	strbuf_release(&reflog_msg);