feat: add rsync-compatible fsync

tests/test_client_cli.c

@@ -339,6 +339,17 @@ static void test_parse_args_archive() {
   config_delete(cfg);
 }
 
+static void test_parse_args_fsync() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--fsync", "/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->use_fsync);
+  config_delete(cfg);
+}
+
 void test_client_cli() {
   test_validate_config_required_paths();
   test_validate_config_incompatible_options();
@@ -360,4 +371,5 @@ void test_client_cli() {
   test_parse_args_unknown_option();
   test_parse_args_rejects_unimplemented_options();
   test_parse_args_archive();
+  test_parse_args_fsync();
 }

tests/test_config.c

@@ -124,6 +124,7 @@ 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->compression_level = 5;
   send_cfg->chunk_size = 1024;
 
@@ -160,6 +161,8 @@ static void test_config_send_receive() {
         ok = false;
       if (recv_cfg->chunk_size != 1024)
         ok = false;
+      if (!recv_cfg->use_fsync)
+        ok = false;
     }
     config_delete(recv_cfg);
     close(p[0]);

tests/test_file.c

@@ -108,6 +108,17 @@ static void test_file_write_to_disk_basic() {
   unlink("test_file_write_to_disk_basic.txt");
 }
 
+static void test_file_write_to_disk_with_fsync() {
+  const char* path = "test_file_write_to_disk_fsync.txt";
+  const char* content = "fsync file content";
+  EXPECT_TRUE(
+      file_to_disk_secure_with_fsync(path, content, strlen(content), false, false, NULL, true));
+  struct stat st;
+  EXPECT_EQ_INT(stat(path, &st), 0);
+  EXPECT_EQ_INT((int)st.st_size, (int)strlen(content));
+  unlink(path);
+}
+
 static void test_file_write_to_disk_creates_dirs() {
   const char* content = "Nested dir test";
   EXPECT_TRUE(file_write_to_disk("test_nested_tmp/nested/file.txt", content, strlen(content), false,
@@ -459,6 +470,7 @@ void test_file() {
   test_file_load_data_missing_file();
   test_file_save_to_disk();
   test_file_write_to_disk_basic();
+  test_file_write_to_disk_with_fsync();
   test_file_write_to_disk_creates_dirs();
   test_file_write_to_disk_does_not_follow_symlink();
   test_file_content_to_buffer();