get_remote_heads: convert to struct object_id

Replace an unsigned char array with struct object_id and express several
hard-coded constants in terms of GIT_SHA1_HEXSZ.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>

connect.c

@@ -120,7 +120,7 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 	*list = NULL;
 	for (;;) {
 		struct ref *ref;
-		unsigned char old_sha1[20];
+		struct object_id old_oid;
 		char *name;
 		int len, name_len;
 		char *buffer = packet_buffer;
@@ -139,34 +139,36 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
 		if (len > 4 && skip_prefix(buffer, "ERR ", &arg))
 			die("remote error: %s", arg);
 
-		if (len == 48 && skip_prefix(buffer, "shallow ", &arg)) {
-			if (get_sha1_hex(arg, old_sha1))
+		if (len == GIT_SHA1_HEXSZ + strlen("shallow ") &&
+			skip_prefix(buffer, "shallow ", &arg)) {
+			if (get_oid_hex(arg, &old_oid))
 				die("protocol error: expected shallow sha-1, got '%s'", arg);
 			if (!shallow_points)
 				die("repository on the other end cannot be shallow");
-			sha1_array_append(shallow_points, old_sha1);
+			sha1_array_append(shallow_points, old_oid.hash);
 			continue;
 		}
 
-		if (len < 42 || get_sha1_hex(buffer, old_sha1) || buffer[40] != ' ')
+		if (len < GIT_SHA1_HEXSZ + 2 || get_oid_hex(buffer, &old_oid) ||
+			buffer[GIT_SHA1_HEXSZ] != ' ')
 			die("protocol error: expected sha/ref, got '%s'", buffer);
-		name = buffer + 41;
+		name = buffer + GIT_SHA1_HEXSZ + 1;
 
 		name_len = strlen(name);
-		if (len != name_len + 41) {
+		if (len != name_len + GIT_SHA1_HEXSZ + 1) {
 			free(server_capabilities);
 			server_capabilities = xstrdup(name + name_len + 1);
 		}
 
 		if (extra_have && !strcmp(name, ".have")) {
-			sha1_array_append(extra_have, old_sha1);
+			sha1_array_append(extra_have, old_oid.hash);
 			continue;
 		}
 
 		if (!check_ref(name, flags))
 			continue;
-		ref = alloc_ref(buffer + 41);
-		hashcpy(ref->old_oid.hash, old_sha1);
+		ref = alloc_ref(buffer + GIT_SHA1_HEXSZ + 1);
+		oidcpy(&ref->old_oid, &old_oid);
 		*list = ref;
 		list = &ref->next;
 		got_at_least_one_head = 1;