feat: add ignore-times incremental option

src/client/client_cli.c

@@ -139,6 +139,7 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--dry-run", "-n", OPT_FLAG, offsetof(Config, dry_run)},
     {"--delete", NULL, OPT_FLAG, offsetof(Config, use_delete)},
     {"--incremental", NULL, OPT_FLAG, offsetof(Config, use_incremental)},
+    {"--ignore-times", "-I", OPT_FLAG, offsetof(Config, ignore_times)},
     {"--delta", NULL, OPT_FLAG, offsetof(Config, use_delta)},
     {"--save-to-disk", NULL, OPT_FLAG, offsetof(Config, save_to_disk)},
     {"--progress", NULL, OPT_FLAG, offsetof(Config, show_progress)},

src/client/usage.c

@@ -28,6 +28,7 @@ void print_usage(void) {
   printf("  --max-size <n>      Skip files larger than n bytes\n");
   printf("  --min-size <n>      Skip files smaller than n bytes\n");
   printf("  --incremental       Skip files unchanged since last transfer\n");
+  printf("  -I, --ignore-times  Transfer files even when size and mtime match\n");
   printf("  --delta             Delta transfer for changed files (requires --incremental)\n");
   printf("  --delta-block <n>   Delta block size in bytes (default: %d)\n",
          DELTA_BLOCK_SIZE_DEFAULT);

src/server/receiver.c

@@ -60,7 +60,7 @@ static bool receiver_process_batch(Config* config, int file_descriptor) {
     }
     struct stat st;
     bool has_old = file_stat_secure(full_path, &st);
-    bool match = has_old && (unsigned long long)st.st_size == check_size &&
+    bool match = !config->ignore_times && has_old && (unsigned long long)st.st_size == check_size &&
                  (long long)st.st_mtime == check_mtime;
     bool sent = send_status(file_descriptor, match ? STATUS_OK : STATUS_NEXT);
     free(full_path);

src/server/server.c

@@ -174,7 +174,8 @@ int receive_files(Config* config, int fd) {
           return -1;
         }
         bool has_old = full_path && file_stat_secure(full_path, &st);
-        bool match = has_old && (unsigned long long)st.st_size == check_size &&
+        bool match = !config->ignore_times && has_old &&
+                     (unsigned long long)st.st_size == check_size &&
                      (long long)st.st_mtime == check_mtime;
         bool sent = send_status(fd, match ? STATUS_OK : STATUS_NEXT);
         free(full_path);

src/shared/config.c

@@ -34,6 +34,7 @@ static void config_set_defaults(Config* config) {
   config->max_size = 0;
   config->min_size = 0;
   config->use_incremental = false;
+  config->ignore_times = false;
   config->use_delta = false;
   config->delta_block_size = DELTA_BLOCK_SIZE_DEFAULT;
   config->delta_max_file_size = DELTA_MAX_FILE_SIZE;
@@ -118,9 +119,9 @@ static bool validate_received_config(const Config* config) {
          valid_wire_bool(config->use_compression) && valid_wire_bool(config->use_metadata) &&
          valid_wire_bool(config->use_sendfile) && valid_wire_bool(config->use_delete) &&
          valid_wire_bool(config->use_incremental) && valid_wire_bool(config->use_delta) &&
-         valid_wire_bool(config->backup) && valid_wire_bool(config->follow_symlinks) &&
+         valid_wire_bool(config->ignore_times) && valid_wire_bool(config->backup) &&
-         valid_wire_bool(config->copy_links) && valid_wire_bool(config->safe_links) &&
+         valid_wire_bool(config->follow_symlinks) && valid_wire_bool(config->copy_links) &&
-         valid_wire_bool(config->copy_unsafe_links) &&
+         valid_wire_bool(config->safe_links) && valid_wire_bool(config->copy_unsafe_links) &&
          valid_wire_bool(config->preserve_hard_links) && valid_wire_bool(config->preserve_acls) &&
          valid_wire_bool(config->preserve_xattrs) && valid_wire_bool(config->preserve_devices) &&
          valid_wire_bool(config->preserve_sparse) && valid_wire_bool(config->update) &&
@@ -228,7 +229,7 @@ static bool send_core_fields(int fd, const Config* c) {
 
 static bool send_delta_fields(int fd, const Config* c) {
   return send_int(fd, c->use_delete) && send_int(fd, c->use_incremental) &&
-         send_int(fd, c->use_delta) &&
+         send_int(fd, c->ignore_times) && send_int(fd, c->use_delta) &&
          send_n_data(fd, &c->delta_block_size, sizeof(c->delta_block_size)) &&
          send_n_data(fd, &c->delta_max_file_size, sizeof(unsigned long long));
 }
@@ -281,6 +282,8 @@ static bool receive_delta_fields(int fd, Config* c) {
     return false;
   if (!receive_wire_bool(fd, &c->use_incremental))
     return false;
+  if (!receive_wire_bool(fd, &c->ignore_times))
+    return false;
   if (!receive_wire_bool(fd, &c->use_delta))
     return false;
   return receive_n_data(fd, &c->delta_block_size, sizeof(c->delta_block_size)) &&

src/shared/config.h

@@ -34,6 +34,7 @@ typedef struct Config {
   unsigned long long max_size;
   unsigned long long min_size;
   bool use_incremental;
+  bool ignore_times;
   bool use_delta;
   uint32_t delta_block_size;
   unsigned long long delta_max_file_size;

tests/integration/test_features.py

@@ -213,6 +213,26 @@ class TestIncremental:
         with open(received_file, "rb") as f:
             assert f.read() == b"hello world\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)
+        assert result.returncode == 0
+
+        received = get_dest_received_dir(DEST_DIR, SOURCE_DIR)
+        source_file = os.path.join(SOURCE_DIR, "small.txt")
+        received_file = os.path.join(received, "small.txt")
+        source_stat = os.stat(source_file)
+        with open(received_file, "wb") as f:
+            f.write(b"stale data\n")
+        os.utime(received_file, (source_stat.st_atime, source_stat.st_mtime))
+
+        result, _ = run_client(SOURCE_DIR, DEST_DIR,
+                               flags=["-M", "--incremental", "--ignore-times"],
+                               port=shared_server.port)
+        assert result.returncode == 0, f"Ignore-times sync failed: {result.stderr[:200]}"
+        with open(received_file, "rb") as f:
+            assert f.read() == b"hello world\n"
+
 
 class TestDelete:
     def test_delete_removes_extra_files(self, shared_server):

tests/test_client_cli.c

@@ -339,6 +339,24 @@ static void test_parse_args_archive() {
   config_delete(cfg);
 }
 
+static void test_parse_args_ignore_times() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "-I", "/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->ignore_times);
+  config_delete(cfg);
+
+  cfg = config_create();
+  char* long_argv[] = {"fastsync", "--ignore-times", "/src", "/dst"};
+  positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, long_argv, positional_args, &positional_count), 0);
+  EXPECT_TRUE(cfg->ignore_times);
+  config_delete(cfg);
+}
+
 void test_client_cli() {
   test_validate_config_required_paths();
   test_validate_config_incompatible_options();
@@ -360,4 +378,5 @@ void test_client_cli() {
   test_parse_args_unknown_option();
   test_parse_args_rejects_unimplemented_options();
   test_parse_args_archive();
+  test_parse_args_ignore_times();
 }

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->ignore_times = true;
   send_cfg->compression_level = 5;
   send_cfg->chunk_size = 1024;
 
@@ -156,6 +157,8 @@ 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)