3 files changed, 35 insertions, 3 deletions
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 6bb128166..e1a687ad0 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -10,6 +10,7 @@
 #include "remote.h"
 #include "transport.h"
 #include "string-list.h"
+#include "sha1-array.h"
 
 static const char receive_pack_usage[] = "git receive-pack <git-dir>";
 
@@ -731,14 +732,23 @@ static int delete_only(struct command *commands)
 	return 1;
 }
 
-static void add_one_alternate_ref(const struct ref *ref, void *unused)
+static void add_one_alternate_sha1(const unsigned char sha1[20], void *unused)
 {
-	add_extra_ref(".have", ref->old_sha1, 0);
+	add_extra_ref(".have", sha1, 0);
+}
+
+static void collect_one_alternate_ref(const struct ref *ref, void *data)
+{
+	struct sha1_array *sa = data;
+	sha1_array_append(sa, ref->old_sha1);
 }
 
 static void add_alternate_refs(void)
 {
-	for_each_alternate_ref(add_one_alternate_ref, NULL);
+	struct sha1_array sa = SHA1_ARRAY_INIT;
+	for_each_alternate_ref(collect_one_alternate_ref, &sa);
+	sha1_array_for_each_unique(&sa, add_one_alternate_sha1, NULL);
+	sha1_array_clear(&sa);
 }
 
 int cmd_receive_pack(int argc, const char **argv, const char *prefix)
diff --git a/sha1-array.c b/sha1-array.c
index 5b75a5a35..b2f47f98f 100644
--- a/sha1-array.c
+++ b/sha1-array.c
@@ -41,3 +41,19 @@ void sha1_array_clear(struct sha1_array *array)
 	array->alloc = 0;
 	array->sorted = 0;
 }
+
+void sha1_array_for_each_unique(struct sha1_array *array,
+				for_each_sha1_fn fn,
+				void *data)
+{
+	int i;
+
+	if (!array->sorted)
+		sha1_array_sort(array);
+
+	for (i = 0; i < array->nr; i++) {
+		if (i > 0 && !hashcmp(array->sha1[i], array->sha1[i-1]))
+			continue;
+		fn(array->sha1[i], data);
+	}
+}
diff --git a/sha1-array.h b/sha1-array.h
index 15d3b6b98..4499b5dad 100644
--- a/sha1-array.h
+++ b/sha1-array.h
@@ -15,4 +15,10 @@ void sha1_array_sort(struct sha1_array *array);
 int sha1_array_lookup(struct sha1_array *array, const unsigned char *sha1);
 void sha1_array_clear(struct sha1_array *array);
 
+typedef void (*for_each_sha1_fn)(const unsigned char sha1[20],
+				 void *data);
+void sha1_array_for_each_unique(struct sha1_array *array,
+				for_each_sha1_fn fn,
+				void *data);
+
 #endif /* SHA1_ARRAY_H */