cache created test dirs

tests/dir_helpers.py

@@ -253,12 +253,33 @@ class PosixTmpDir(TmpDir, pathlib.PurePosixPath):
     pass
 
 
+CACHE = {}
+
+
 @pytest.fixture(scope="session")
-def make_tmp_dir(tmp_path_factory, request):
-    def make(name, *, scm=False, dvc=False, **kwargs):
+def make_tmp_dir(tmp_path_factory, request, worker_id):
+    def make(name, *, scm=False, dvc=False, subdir=False):
+        from dvc.repo import Repo
+        from dvc.scm.git import Git
+        from dvc.utils.fs import fs_copy
+
+        cache = CACHE.get((scm, dvc, subdir))
+        if not cache:
+            cache = tmp_path_factory.mktemp("dvc-test-cache" + worker_id)
+            TmpDir(cache).init(scm=scm, dvc=dvc, subdir=subdir)
+            CACHE[(scm, dvc, subdir)] = os.fspath(cache)
         path = tmp_path_factory.mktemp(name) if isinstance(name, str) else name
+        for entry in os.listdir(cache):
+            # shutil.copytree's dirs_exist_ok is only available in >=3.8
+            fs_copy(os.path.join(cache, entry), os.path.join(path, entry))
         new_dir = TmpDir(path)
-        new_dir.init(scm=scm, dvc=dvc, **kwargs)
+        str_path = os.fspath(new_dir)
+        if dvc:
+            new_dir.dvc = Repo(str_path)
+        if scm:
+            new_dir.scm = (
+                new_dir.dvc.scm if hasattr(new_dir, "dvc") else Git(str_path)
+            )
         request.addfinalizer(new_dir.close)
         return new_dir