fix(parity): protect -R prefix-relative excluded and size-skipped mirrors

A -R source prune (--exclude/--max-size) must record the destination wire
path below the reconstructed prefix so --delete protects it; the parallel
root scan and the sequential skip path used the source path instead.

src/client/scanner.c

@@ -1289,9 +1289,17 @@ Chunk* directory_scanner_next(DirectoryScanner* scanner) {
          wire path, not its source path (which would not match the destination
          layout and would leave the mirror deletable). */
       if (inspected.excluded) {
-        char* protected_path = scanner->relative_mode
+        char* protected_path;
-                                   ? child_rel_path(scanner->current_rel, entry->d_name)
+        if (scanner->relative_mode) {
-                                   : path_cat(scanner->current_path, entry->d_name);
+          protected_path = child_rel_path(scanner->current_rel, entry->d_name);
+        } else if (scanner->options.relative_prefix) {
+          char* relc = child_rel_path(scanner->current_rel, entry->d_name);
+          protected_path =
+              relc ? scanner_prefix_send_path(scanner->options.relative_prefix, relc) : NULL;
+          free(relc);
+        } else {
+          protected_path = path_cat(scanner->current_path, entry->d_name);
+        }
         if (!protected_path) {
           scanner->failed = true;
           break;
@@ -1753,8 +1761,20 @@ static void scan_root_entry(const ScannerOptions* options, const FilterNode* roo
     bool files_from_prune = options->file_list && !file_list_affects(options->file_list, rel);
     if (!files_from_prune && !use_rel && options->excluded_paths) {
       const char* rel_path = *cur_path == '/' ? cur_path + 1 : cur_path;
+      char* prefixed = NULL;
+      if (options->relative_prefix) {
+        prefixed = scanner_prefix_send_path(options->relative_prefix, entry->d_name);
+        if (!prefixed) {
+          free(rel);
+          free(cur_path);
+          ps->failed = true;
+          return;
+        }
+        rel_path = prefixed;
+      }
       if (!excluded_sink_append(options->excluded_paths, options->excluded_mutex, rel_path))
         ps->failed = true;
+      free(prefixed);
     }
     free(rel);
     free(cur_path);

tests/integration/test_parity_selection.py

@@ -169,6 +169,36 @@ class TestDirsOneLevel:
                 == os.path.isfile(os.path.join(rdst, "unrelated", "keep.txt")))
         assert _tree(dest) == _tree(rdst)
 
+    @requires_rsync
+    @pytest.mark.ci
+    @pytest.mark.parametrize("mt", [False, True])
+    def test_relative_delete_protects_excluded_mirror(self, mt):
+        """-R --delete with --exclude must protect the destination mirror of an
+        excluded source path (recorded as a prefix-relative wire path)."""
+        source = _make_tree(os.path.join(TEST_DATA_DIR, "sel_delexc_src"))
+        with open(os.path.join(source, "foo", "secret.tmp"), "wb") as fh:
+            fh.write(b"secret\n")
+        dest = os.path.join(TEST_DATA_DIR, "sel_delexc_dst")
+        rdst = os.path.join(TEST_DATA_DIR, "sel_delexc_rdst")
+        for root in (dest, rdst):
+            clean_dir(root)
+            os.makedirs(os.path.join(root, "foo"))
+            with open(os.path.join(root, "foo", "secret.tmp"), "wb") as fh:
+                fh.write(b"secret\n")
+            with open(os.path.join(root, "foo", "extra.txt"), "wb") as fh:
+                fh.write(b"extra\n")
+        spec = source + "/./foo"
+        with ServerManager() as server:
+            server.start(extra_args=["--allow-delete"])
+            r = _rsync(["-aR", "--delete", "--exclude=*.tmp", spec, rdst + "/"])
+            assert r.returncode == 0, r.stderr
+            flags = ["-a", "-R", "--delete", "--exclude=*.tmp"] + (["--threads"] if mt else [])
+            result, _ = run_client(spec, dest, flags=flags, port=server.port)
+            assert result.returncode == 0, result.stderr[:300]
+        assert _tree(dest) == _tree(rdst)
+        assert os.path.isfile(os.path.join(dest, "foo", "secret.tmp"))
+        assert not os.path.exists(os.path.join(dest, "foo", "extra.txt"))
+
 
 class TestClientAliases:
     """#5: safe rsync option aliases accepted client-side."""