Merge remote-tracking branch 'origin/feat/existing' into dev

README.md

@@ -104,6 +104,7 @@ partial, alternate, and planned behavior.
 | `--max-size <n>` | Skip files larger than n bytes |
 | `--min-size <n>` | Skip files smaller than n bytes |
 | `--incremental` | Skip files unchanged since last transfer (size + mtime). Auto-enables `--preserve`. Incompatible with `-s`. |
+| `--existing` | Skip files not already present at the destination; update existing files normally. |
 | `--bwlimit <KB/s>` | Bandwidth limit in kilobytes per second |
 | `--chunk-size <n>` | Chunk size in bytes (default: 10485760) |
 | `--timeout <sec>` | I/O timeout in seconds (default: 30) |

RSYNC_COMPAT.md

@@ -10,7 +10,7 @@ This document maps rsync's full feature set to FastSync's current implementation
 | 🔀 Alt Arg | 4 | Functionality exists but under different flag/semantics |
 | ⚠️ Partial | 5 | Flag parsed/stored but behavior incomplete |
 | 🔄 Compatibility No-op | 1 | Flag is accepted for CLI compatibility but has no effect |
-| ❌ Not Implemented | 96 | Flag not recognized or no behavior |
+| ❌ Not Implemented | 95 | Flag not recognized or no behavior |
 | **Total** | **141** | |
 
 ---
@@ -61,7 +61,7 @@ This document maps rsync's full feature set to FastSync's current implementation
 | `-I`, `--ignore-times` | Don't skip files matching size+time | ❌ Not Implemented | |
 | `--size-only` | Skip based on size only | ✅ Implemented | With `--incremental`, ignores mtime |
 | `-@`, `--modify-window=NUM` | Mod-time comparison accuracy | ✅ Implemented | Whole-second tolerance with nanosecond-aware comparisons |
-| `--existing` | Skip creating new files on receiver | ❌ Not Implemented | |
+| `--existing` | Skip creating new files on receiver | ✅ Implemented | Existing destination files continue through normal update handling |
 | `--ignore-existing` | Skip updating existing files | ❌ Not Implemented | |
 | `--remove-source-files` | Sender removes regular files after confirmed transfer | ✅ Implemented | |
 
@@ -248,7 +248,7 @@ Ranked by user demand, implementation complexity, and interoperability impact:
 | 1 | `--whole-file` / `-W` | Low | High — users expect opt-out of delta |
 | 2 | `--ignore-times` / `-I` | Low | Medium — useful for forcing re-transfer |
 | 3 | `--size-only` | Low | Medium — common migration scenario |
-| 4 | `--existing` / `--ignore-existing` | Low | Medium — common sync patterns |
+| 4 | `--ignore-existing` | Low | Medium — common sync patterns |
 | 5 | `--delete-during` | Medium | High — performance improvement |
 | 6 | `--delay-updates` | Medium | High — atomic updates |
 | 7 | `--chmod` | Low | Medium — permission flexibility |

src/client/client_cli.c

@@ -229,6 +229,7 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--fsync", NULL, OPT_FLAG, offsetof(Config, use_fsync)},
     {"--checksum", NULL, OPT_FLAG, offsetof(Config, checksum)},
     {"--8-bit-output", "-8", OPT_FLAG, offsetof(Config, eight_bit_output)},
+    {"--existing", NULL, OPT_FLAG, offsetof(Config, existing)},
 
     {"--source-dir", NULL, OPT_STRING, offsetof(Config, send_directory)},
     {"--dest-dir", NULL, OPT_STRING, offsetof(Config, receive_root_directory)},

src/client/usage.c

@@ -34,6 +34,7 @@ void print_usage(void) {
   printf("  -I, --ignore-times  Transfer files even when size and mtime match\n");
   printf("  -@, --modify-window <sec>  Modification time tolerance\n");
   printf("  -u, --update        Skip files newer than the source on receiver\n");
+  printf("  --existing          Skip files not already present at destination\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",

src/shared/config.c

@@ -74,6 +74,7 @@ static void config_set_defaults(Config* config) {
   config->list_only = false;
   config->human_readable = false;
   config->eight_bit_output = false;
+  config->existing = false;
   config->update = false;
   config->inplace = false;
   config->use_fsync = false;
@@ -130,9 +131,10 @@ static bool validate_received_config(const Config* config) {
          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) &&
-         valid_wire_bool(config->inplace) && valid_wire_bool(config->append) &&
-         valid_wire_bool(config->use_fsync) && valid_wire_bool(config->append_verify) &&
+         valid_wire_bool(config->preserve_sparse) && valid_wire_bool(config->existing) &&
+         valid_wire_bool(config->update) && valid_wire_bool(config->inplace) &&
+         valid_wire_bool(config->append) && valid_wire_bool(config->use_fsync) &&
+         valid_wire_bool(config->append_verify) &&
          valid_wire_bool(config->delete_excluded) && valid_wire_bool(config->delete_after) &&
          valid_wire_bool(config->relative) && valid_wire_bool(config->prune_empty_dirs) &&
          valid_wire_bool(config->partial) && valid_wire_bool(config->delete_before) &&
@@ -255,8 +257,9 @@ static bool send_file_options(int fd, const Config* c) {
 }
 
 static bool send_selection_options(int fd, const Config* c) {
-  return send_int(fd, c->update) && send_int(fd, c->inplace) && send_int(fd, c->append) &&
-         send_int(fd, c->use_fsync) && send_int(fd, c->append_verify) &&
+  return send_int(fd, c->existing) && send_int(fd, c->update) && send_int(fd, c->inplace) &&
+         send_int(fd, c->append) && send_int(fd, c->use_fsync) &&
+         send_int(fd, c->append_verify) &&
          send_int(fd, c->delete_excluded) && send_int(fd, c->delete_after) &&
          send_n_data(fd, &c->max_delete, sizeof(c->max_delete)) && send_int(fd, c->relative) &&
          send_int(fd, c->prune_empty_dirs);
@@ -325,7 +328,8 @@ static bool receive_file_options(int fd, Config* c) {
 }
 
 static bool receive_selection_options(int fd, Config* c) {
-  bool* flags[] = {&c->update,        &c->inplace,         &c->append,      &c->use_fsync,
+  bool* flags[] = {&c->existing,      &c->update,          &c->inplace,     &c->append,
+                   &c->use_fsync,
                    &c->append_verify, &c->delete_excluded, &c->delete_after};
   for (size_t i = 0; i < sizeof(flags) / sizeof(flags[0]); i++) {
     if (!receive_wire_bool(fd, flags[i]))

src/shared/config.h

@@ -82,6 +82,7 @@ typedef struct Config {
   bool eight_bit_output;
 
   // Issue #127: Transfer modes
+  bool existing;
   bool update;
   bool inplace;
   bool use_fsync;

src/shared/file_receive.c

@@ -29,6 +29,7 @@ bool file_save_to_disk(const char* root_directory, const File* file, const Confi
   const char* backup_dir = (config && config->backup_dir) ? config->backup_dir : NULL;
   const char* partial_dir = (config && config->partial_dir) ? config->partial_dir : NULL;
   char *confined_backup = NULL, *confined_partial = NULL, *disk_path = NULL;
+  char* destination_path = NULL;
   char *backup_path = NULL, *parent_copy = NULL;
 
   if (!file || !file->path || !file->data || (file->data->size != 0 && !file->data->data) ||
@@ -54,13 +55,27 @@ bool file_save_to_disk(const char* root_directory, const File* file, const Confi
 
   const char* actual_root =
       (partial_dir && config && config->partial) ? confined_partial : root_directory;
+  destination_path = path_cat(root_directory, file->path);
   disk_path = path_cat(actual_root, file->path);
-  if (disk_path == NULL) {
+  if (destination_path == NULL || disk_path == NULL) {
     free(confined_backup);
     free(confined_partial);
+    free(destination_path);
+    free(disk_path);
     return false;
   }
 
+  /* --existing checks the final destination, not a temporary partial path. */
+  if (config && config->existing && !file_path_exists_secure(destination_path)) {
+    free(confined_backup);
+    free(confined_partial);
+    free(destination_path);
+    free(disk_path);
+    return true;
+  }
+  free(destination_path);
+  destination_path = NULL;
+
   /* --update is receiver-side policy: never replace a newer destination.
      The secure stat does not require read permission on the destination. */
   if (config && config->update && file_destination_is_newer_secure(disk_path, file->metadata)) {
@@ -110,6 +125,7 @@ bool file_save_to_disk(const char* root_directory, const File* file, const Confi
   free(backup_path);
   free(confined_backup);
   free(confined_partial);
+  free(destination_path);
   free(disk_path);
   return ok;
 
@@ -118,6 +134,7 @@ fail:
   free(backup_path);
   free(confined_backup);
   free(confined_partial);
+  free(destination_path);
   free(disk_path);
   return false;
 }

tests/integration/test_features.py

@@ -412,66 +412,6 @@ class TestIncremental:
         mismatches, missing = verify_transfer(SOURCE_DIR, received)
         assert not missing, f"Missing: {missing}"
         assert not mismatches, f"Mismatch: {mismatches}"
-        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"
-
-    def test_modify_window_allows_subsecond_mtime_difference(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"modified!!!\n")
-        os.utime(received_file, ns=(source_stat.st_atime_ns,
-                                    source_stat.st_mtime_ns - 1500000000))
-
-        result, _ = run_client(SOURCE_DIR, DEST_DIR,
-                               flags=["-M", "--incremental", "--modify-window=2"],
-                               port=shared_server.port)
-        assert result.returncode == 0, f"Modify-window sync failed: {result.stderr[:200]}"
-        with open(received_file, "rb") as f:
-            assert f.read() == b"modified!!!\n"
-
-    def test_whole_file_disables_delta_and_keeps_compression(self, shared_server):
-        clean_dir(DEST_DIR)
-        result, _ = run_client(SOURCE_DIR, DEST_DIR, flags=["-M"], port=shared_server.port)
-        assert result.returncode == 0
-
-        source_file = os.path.join(SOURCE_DIR, "medium.txt")
-        with open(source_file, "wb") as f:
-            f.write(b"whole-file replacement\n" * 5000)
-
-        result, _ = run_client(
-            SOURCE_DIR,
-            DEST_DIR,
-            flags=["-M", "--incremental", "--delta", "-W", "-c"],
-            port=shared_server.port,
-        )
-        assert result.returncode == 0, f"Whole-file sync failed: {(result.stderr or result.stdout)[:200]}"
-        received = get_dest_received_dir(DEST_DIR, SOURCE_DIR)
-        mismatches, missing = verify_transfer(SOURCE_DIR, received)
-        assert not missing, f"Missing: {missing}"
-        assert not mismatches, f"Mismatch: {mismatches}"
 
 
 class TestUpdate:
@@ -529,6 +469,34 @@ class TestUpdate:
             assert f.read() == b"hello world\n"
 
 
+class TestExisting:
+    def test_existing_updates_existing_and_skips_new(self, shared_server):
+        clean_dir(DEST_DIR)
+        result, _ = run_client(SOURCE_DIR, DEST_DIR, flags=["-M"], port=shared_server.port)
+        assert result.returncode == 0, f"Initial sync failed: {(result.stderr or result.stdout)[:200]}"
+
+        received = get_dest_received_dir(DEST_DIR, SOURCE_DIR)
+        source_file = os.path.join(SOURCE_DIR, "small.txt")
+        new_source_file = os.path.join(SOURCE_DIR, "new-existing-test.txt")
+        with open(source_file, "wb") as f:
+            f.write(b"updated existing content\n")
+        with open(new_source_file, "wb") as f:
+            f.write(b"this file must not be created\n")
+
+        try:
+            result, _ = run_client(SOURCE_DIR, DEST_DIR,
+                                   flags=["-M", "--existing"], port=shared_server.port)
+            assert result.returncode == 0, f"--existing sync failed: {(result.stderr or result.stdout)[:200]}"
+
+            with open(os.path.join(received, "small.txt"), "rb") as f:
+                assert f.read() == b"updated existing content\n"
+            assert not os.path.exists(os.path.join(received, "new-existing-test.txt"))
+        finally:
+            os.unlink(new_source_file)
+            with open(source_file, "wb") as f:
+                f.write(b"hello world\n")
+
+
 class TestDelete:
     def test_delete_removes_extra_files(self, shared_server):
         clean_dir(DEST_DIR)

tests/test_client_cli.c

@@ -504,6 +504,17 @@ static void test_parse_args_fsync() {
   config_delete(cfg);
 }
 
+static void test_parse_args_existing() {
+  Config* cfg = config_create();
+  char* argv[] = {"fastsync", "--existing", "/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->existing);
+  config_delete(cfg);
+}
+
 static void test_parse_args_ignore_times() {
   Config* cfg = config_create();
   char* argv[] = {"fastsync", "-I", "/src", "/dst"};
@@ -649,6 +660,7 @@ void test_client_cli() {
   test_parse_args_update();
   test_parse_args_archive();
   test_parse_args_fsync();
+  test_parse_args_existing();
   test_parse_args_ignore_times();
   test_parse_args_8_bit_output();
   test_parse_args_stderr_modes();

tests/test_config.c

@@ -132,6 +132,7 @@ static void test_config_send_receive() {
   send_cfg->chunk_size = 1024;
   send_cfg->eight_bit_output = true;
   send_cfg->modify_window = 4;
+  send_cfg->existing = true;
 
   /* Use socketpair for bidirectional communication */
   int p[2];
@@ -178,6 +179,8 @@ static void test_config_send_receive() {
         ok = false;
       if (recv_cfg->modify_window != 4)
         ok = false;
+      if (!recv_cfg->existing)
+        ok = false;
     }
     config_delete(recv_cfg);
     close(p[0]);

tests/test_file.c

@@ -113,6 +113,50 @@ static void test_file_save_to_disk_with_fsync_config() {
   rmdir("test_save_fsync_tmp");
 }
 
+static void test_file_save_to_disk_existing() {
+  const char* root = "test_existing_tmp";
+  const char* existing_path = "test_existing_tmp/existing.txt";
+  const char* missing_path = "test_existing_tmp/missing.txt";
+  EXPECT_TRUE(file_write_to_disk(existing_path, "old", 3, false, false));
+
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  cfg->existing = true;
+
+  File* existing = file_create("existing.txt");
+  EXPECT_NOT_NULL(existing);
+  existing->data->data = malloc(3);
+  EXPECT_NOT_NULL(existing->data->data);
+  memcpy(existing->data->data, "new", 3);
+  existing->data->size = 3;
+  EXPECT_TRUE(file_save_to_disk(root, existing, cfg));
+  file_destroy(existing);
+
+  File* missing = file_create("missing.txt");
+  EXPECT_NOT_NULL(missing);
+  missing->data->data = malloc(7);
+  EXPECT_NOT_NULL(missing->data->data);
+  memcpy(missing->data->data, "skipped", 7);
+  missing->data->size = 7;
+  EXPECT_TRUE(file_save_to_disk(root, missing, cfg));
+  file_destroy(missing);
+
+  FILE* fp = fopen(existing_path, "rb");
+  char content[4] = {0};
+  EXPECT_NOT_NULL(fp);
+  // cppcheck-suppress knownConditionTrueFalse
+  if (fp) {
+    EXPECT_EQ_INT((int)fread(content, 1, 3, fp), 3);
+    fclose(fp);
+  }
+  EXPECT_EQ_STR(content, "new");
+  EXPECT_EQ_INT(access(missing_path, F_OK), -1);
+
+  config_delete(cfg);
+  unlink(existing_path);
+  rmdir(root);
+}
+
 static void test_file_write_to_disk_basic() {
   const char* content = "Basic file_write_to_disk test";
   EXPECT_TRUE(file_write_to_disk("test_file_write_to_disk_basic.txt", content, strlen(content),
@@ -495,6 +539,7 @@ void test_file() {
   test_file_load_data_missing_file();
   test_file_save_to_disk();
   test_file_save_to_disk_with_fsync_config();
+  test_file_save_to_disk_existing();
   test_file_write_to_disk_basic();
   test_file_write_to_disk_with_fsync();
   test_file_write_to_disk_creates_dirs();