Merge remote-tracking branch 'origin/feat/modify-window' into dev

# Conflicts:
#	RSYNC_COMPAT.md
#	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
#	src/shared/file_receive.c
#	tests/integration/test_features.py
#	tests/test_client_cli.c
#	tests/test_config.c

src/client/client_cli.c

@@ -208,6 +208,7 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--incremental", NULL, OPT_FLAG, offsetof(Config, use_incremental)},
     {"--size-only", NULL, OPT_FLAG, offsetof(Config, size_only)},
     {"--ignore-times", "-I", OPT_FLAG, offsetof(Config, ignore_times)},
+    {"--modify-window", "-@", OPT_NONNEG_INT, offsetof(Config, modify_window)},
     {"--delta", NULL, OPT_FLAG, offsetof(Config, use_delta)},
     {"--whole-file", "-W", OPT_FLAG, offsetof(Config, whole_file)},
     {"--save-to-disk", NULL, OPT_FLAG, offsetof(Config, save_to_disk)},
@@ -292,6 +293,18 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
   bool verbose = false;
   protocol_set_8_bit_output(config->eight_bit_output);
   for (int i = 1; i < argc; i++) {
+    const char* modify_window_prefix = "--modify-window=";
+    if (strncmp(argv[i], modify_window_prefix, strlen(modify_window_prefix)) == 0) {
+      if (set_nonneg_int_option(&config->modify_window, argv[i] + strlen(modify_window_prefix),
+                                "--modify-window") != 0)
+        return -1;
+      continue;
+    }
+    if (strncmp(argv[i], "-@", 2) == 0 && argv[i][2] != '\0') {
+      if (set_nonneg_int_option(&config->modify_window, argv[i] + 2, "-@") != 0)
+        return -1;
+      continue;
+    }
     const OptionEntry* entry = find_table_option(argv[i]);
     if (entry) {
       if (entry->kind != OPT_FLAG) {

src/client/client_send.c

@@ -286,10 +286,13 @@ static int incremental_check(Client* client, File* file, const Config* config,
     return -1;
   unsigned long long fsize = file->data->size;
   long long mtime = file->metadata ? file->metadata->mtime_sec : 0;
+  long long mtime_nsec = file->metadata ? file->metadata->mtime_nsec : 0;
   if (!send_n_data(client->file_descriptor, &fsize, sizeof(fsize)))
     return -1;
   if (!send_n_data(client->file_descriptor, &mtime, sizeof(mtime)))
     return -1;
+  if (!send_n_data(client->file_descriptor, &mtime_nsec, sizeof(mtime_nsec)))
+    return -1;
   if (config->checksum) {
     uint64_t checksum;
     if (!file_checksum(file, &checksum) ||

src/client/usage.c

@@ -32,6 +32,7 @@ void print_usage(void) {
   printf("  --incremental       Skip files unchanged since last transfer\n");
   printf("  --size-only         Skip incremental files matching in size, ignoring mtime\n");
   printf("  -I, --ignore-times  Transfer files even when size and mtime match\n");
+  printf("  -@, --modify-window <sec>  Modification time tolerance\n");
   printf("  --delta             Delta transfer for changed files (requires --incremental)\n");
   printf("  -W, --whole-file    Transfer changed files without delta processing\n");
   printf("  --delta-block <n>   Delta block size in bytes (default: %d)\n",