pack: move find_sha1_pack()

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

packfile.c

@@ -1774,3 +1774,16 @@ int is_pack_valid(struct packed_git *p)
 	/* Force the pack to open to prove its valid. */
 	return !open_packed_git(p);
 }
+
+struct packed_git *find_sha1_pack(const unsigned char *sha1,
+				  struct packed_git *packs)
+{
+	struct packed_git *p;
+
+	for (p = packs; p; p = p->next) {
+		if (find_pack_entry_one(sha1, p))
+			return p;
+	}
+	return NULL;
+
+}