Merge remote-tracking branch 'origin/feat/size-only' into dev

# Conflicts:
#	src/client/client_cli.c
#	src/client/usage.c
#	src/server/receiver.c
#	src/server/server.c
#	src/shared/config.c
#	src/shared/config.h
#	tests/integration/test_features.py
#	tests/test_config.c

tests/integration/test_features.py

@@ -331,6 +331,26 @@ class TestIncremental:
         with open(received_file, "rb") as f:
             assert f.read() == b"hello world\n"
 
+    def test_size_only_skips_same_size_with_different_mtime(self, shared_server):
+        clean_dir(DEST_DIR)
+        result, _ = run_client(SOURCE_DIR, DEST_DIR, flags=["-M"], port=shared_server.port)
+        assert result.returncode == 0
+
+        received = get_dest_received_dir(DEST_DIR, SOURCE_DIR)
+        received_file = os.path.join(received, "small.txt")
+        with open(received_file, "wb") as f:
+            f.write(b"different!!\n")
+        os.utime(received_file, (time.time() - 3600, time.time() - 3600))
+
+        result, _ = run_client(
+            SOURCE_DIR, DEST_DIR,
+            flags=["-M", "--incremental", "--size-only"],
+            port=shared_server.port,
+        )
+        assert result.returncode == 0, f"Size-only sync failed: {result.stderr[:200]}"
+        with open(received_file, "rb") as f:
+            assert f.read() == b"different!!\n"
+
     def test_ignore_times_transfers_same_size_and_mtime(self, shared_server):
         clean_dir(DEST_DIR)
         result, _ = run_client(SOURCE_DIR, DEST_DIR, flags=["-M"], port=shared_server.port)

tests/test_client_cli.c

@@ -210,6 +210,20 @@ static void test_parse_args_valid_port() {
   config_delete(cfg);
 }
 
+/* Test parse_args with --size-only. */
+static void test_parse_args_size_only() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--size-only", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), 0);
+  EXPECT_TRUE(cfg->size_only);
+  EXPECT_EQ_INT(positional_count, 2);
+
+  config_delete(cfg);
+}
+
 /* Test parse_args rejects port > 65535 */
 static void test_parse_args_invalid_port() {
   Config* cfg = config_create();
@@ -568,6 +582,7 @@ void test_client_cli() {
   test_parse_args_help();
   test_parse_args_version();
   test_parse_args_valid_port();
+  test_parse_args_size_only();
   test_parse_args_invalid_port();
   test_parse_args_non_numeric_port();
   test_parse_args_invalid_server_port();

tests/test_config.c

@@ -124,10 +124,10 @@ static void test_config_send_receive() {
   send_cfg->use_chunk_serialization = true;
   send_cfg->use_compression = true;
   send_cfg->use_metadata = true;
-  send_cfg->use_fsync = true;
   send_cfg->use_delta = true;
   send_cfg->whole_file = true;
   send_cfg->ignore_times = true;
+  send_cfg->size_only = true;
   send_cfg->compression_level = 5;
   send_cfg->chunk_size = 1024;
   send_cfg->eight_bit_output = true;
@@ -161,13 +161,13 @@ static void test_config_send_receive() {
         ok = false;
       if (!recv_cfg->use_chunk_serialization)
         ok = false;
-      if (!recv_cfg->ignore_times)
-        ok = false;
       if (recv_cfg->compression_level != 5)
         ok = false;
       if (recv_cfg->chunk_size != 1024)
         ok = false;
-      if (!recv_cfg->use_fsync)
+      if (!recv_cfg->size_only)
+        ok = false;
+      if (!recv_cfg->ignore_times)
         ok = false;
       if (!recv_cfg->eight_bit_output)
         ok = false;
@@ -200,11 +200,11 @@ static void test_config_send_receive() {
 }
 
 static void test_config_send_receive_version_mismatch() {
-  /* Create a config with a different protocol version */
+  /* A peer using the previous wire format must be rejected. */
   Config* cfg = config_create();
   EXPECT_NOT_NULL(cfg);
   free(cfg->version);
-  cfg->version = str_dup("0.0");
+  cfg->version = str_dup("2.2.0");
   cfg->send_directory = str_dup("/src");
   cfg->receive_root_directory = str_dup("/dst");