feat: add rsync-compatible chmod option

tests/integration/test_features.py

@@ -52,6 +52,22 @@ class TestArchiveMode:
         assert not mismatches, f"Mismatch: {mismatches}"
 
 
+class TestChmod:
+    def test_chmod_applies_to_transferred_files(self, shared_server):
+        clean_dir(DEST_DIR)
+        source_file = os.path.join(SOURCE_DIR, "small.txt")
+        os.chmod(source_file, 0o777)
+        result, dur = run_client(
+            SOURCE_DIR, DEST_DIR,
+            flags=["--chmod=u=rw,go=r"],
+            port=shared_server.port,
+        )
+        if result.returncode != 0:
+            pytest.fail(f"Exit {result.returncode}: {(result.stderr or result.stdout)[:200]}")
+        received = get_dest_received_dir(DEST_DIR, SOURCE_DIR)
+        assert (os.stat(os.path.join(received, "small.txt")).st_mode & 0o777) == 0o644
+
+
 class TestExclude:
     def test_exclude_single(self, shared_server):
         clean_dir(DEST_DIR)

tests/test_client_cli.c

@@ -1,5 +1,6 @@
 #include "test_client_cli.h"
 #include "client_validation.h"
+#include "chmod.h"
 #include "config.h"
 #include "test_utils.h"
 #include "utils.h"
@@ -181,6 +182,29 @@ static void test_parse_args_valid_port() {
   config_delete(cfg);
 }
 
+static void test_parse_args_chmod() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--chmod=u=rw,go=r", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), 0);
+  EXPECT_EQ_STR(cfg->chmod_spec, "u=rw,go=r");
+  EXPECT_TRUE(cfg->use_metadata);
+  mode_t result;
+  EXPECT_TRUE(chmod_apply(0777, cfg->chmod_spec, &result));
+  EXPECT_EQ_INT(result, 0644);
+  config_delete(cfg);
+}
+
+static void test_parse_args_rejects_invalid_chmod() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--chmod=a+X", "/src", "/dst"};
+  int positional_args[2];
+  int positional_count = 0;
+  EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), -1);
+  config_delete(cfg);
+}
+
 /* Test parse_args rejects port > 65535 */
 static void test_parse_args_invalid_port() {
   Config* cfg = config_create();
@@ -352,6 +376,8 @@ void test_client_cli() {
   test_parse_args_help();
   test_parse_args_version();
   test_parse_args_valid_port();
+  test_parse_args_chmod();
+  test_parse_args_rejects_invalid_chmod();
   test_parse_args_invalid_port();
   test_parse_args_non_numeric_port();
   test_parse_args_invalid_server_port();

tests/test_metadata.c

@@ -1,4 +1,5 @@
 #include "test_metadata.h"
+#include "chmod.h"
 #include "metadata.h"
 #include "protocol.h"
 #include "test_utils.h"
@@ -144,6 +145,18 @@ static void test_file_restore_metadata() {
   unlink(path);
 }
 
+static void test_chmod_changes() {
+  mode_t result;
+  EXPECT_TRUE(chmod_apply(0777, "u=rw,go=r", &result));
+  EXPECT_EQ_INT(result, 0644);
+  EXPECT_TRUE(chmod_apply(0644, "a+x", &result));
+  EXPECT_EQ_INT(result, 0755);
+  EXPECT_TRUE(chmod_apply(0777, "755", &result));
+  EXPECT_EQ_INT(result, 0755);
+  EXPECT_FALSE(chmod_apply(0777, "a+X", &result));
+  EXPECT_FALSE(chmod_apply(0777, "a+r,", &result));
+}
+
 void test_metadata() {
   test_metadata_to_from_buf_roundtrip();
   test_metadata_to_buf_null();
@@ -152,4 +165,5 @@ void test_metadata() {
   test_metadata_send_null();
   test_metadata_rejects_invalid_values();
   test_file_restore_metadata();
+  test_chmod_changes();
 }