fix(parity): rsync 3.4.1 symlink and special-node semantics (#287, #288)

#287:
- --safe-links: keep safe in-tree links AS symlinks and skip unsafe
  (absolute or ".."-escaping) ones, mirroring rsync's unsafe_symlink().
  Skipped links are recorded as delete-protected so --delete does not
  remove their destination mirror (no silent data loss).
- --copy-unsafe-links: preserve safe links as symlinks and dereference
  only unsafe ones.
- --munge-links: receiver-side rewrite storing /rsyncd-munged/-prefixed
  targets (rsync parity), replacing the no-op #SYMLINK sender prefix.
- -l: store the target verbatim, including absolute and ".." targets
  (rsync -l parity); the old receiver containment silently dropped them.

#288:
- --specials: recreate unix-domain sockets via mknod(S_IFSOCK), which
  Linux permits unprivileged; keep EEXIST/EPERM skip behavior.
- --copy-devices: copy a device's content into a regular file when
  requested; skip unrequested non-regular entries like rsync's default.

tests/test_server.c

@@ -818,10 +818,24 @@ static void test_special_socket_path_log_escaped() {
   set_log_level(LOG_LEVEL_WARNING);
   log_set_8_bit_output(false);
 
+  const char* root = "test_special_sock_escape_root";
+  const char* existing = "test_special_sock_escape_root/evil\npath";
+  unlink(existing);
+  rmdir(root);
+  EXPECT_EQ_INT(mkdir(root, 0700), 0);
+  FILE* planted = fopen(existing, "wb");
+  EXPECT_NOT_NULL(planted);
+  fclose(planted);
+
   FILE* capture = tmpfile();
   EXPECT_NOT_NULL(capture);
   log_set_file(capture);
 
+  Config* cfg = config_create();
+  EXPECT_NOT_NULL(cfg);
+  cfg->preserve_specials = true;
+  cfg->use_metadata = true;
+
   File* file = file_create("evil\npath");
   EXPECT_NOT_NULL(file);
   file->is_special = true;
@@ -829,7 +843,9 @@ static void test_special_socket_path_log_escaped() {
   EXPECT_NOT_NULL(file->metadata);
   file->metadata->mode = S_IFSOCK | 0644;
 
-  FileSaveResult result = file_save_to_disk_full("/tmp/dst", file, NULL);
+  /* A non-matching entry already occupies the path: the socket creation is
+     refused and the warning must escape the path's control byte. */
+  FileSaveResult result = file_save_to_disk_full(root, file, cfg);
   EXPECT_EQ_INT(result, FILE_SAVE_SKIPPED);
 
   fflush(capture);
@@ -841,8 +857,11 @@ static void test_special_socket_path_log_escaped() {
   log_set_file(NULL);
   fclose(capture);
   file_destroy(file);
+  config_delete(cfg);
+  unlink(existing);
+  rmdir(root);
 
-  EXPECT_NOT_NULL(strstr(output, "socket not recreated: evil\\#012path"));
+  EXPECT_NOT_NULL(strstr(output, "refusing to replace existing entry with socket: evil\\#012path"));
 }
 
 /* B1: a client-planted FIFO at the destination must not block the receiver's