brancher: add trace when switching filesystem (#9022)

brancher: add trace info when switching filesystem

dvc/repo/__init__.py

@@ -583,17 +583,14 @@ class Repo:
         if self._data_index is not None:
             self._data_index.close()
 
-    def _reset_cached_indecies(self):
+    def _reset(self):
+        self.scm._reset()  # pylint: disable=protected-access
+        self.state.close()
         self.__dict__.pop("index", None)
         self.__dict__.pop("dvcignore", None)
         self.__dict__.pop("dvcfs", None)
         self.__dict__.pop("datafs", None)
 
-    def _reset(self):
-        self.state.close()
-        self.scm._reset()  # pylint: disable=protected-access
-        self._reset_cached_indecies()
-
     def __enter__(self):
         return self
 

dvc/repo/brancher.py

@@ -1,7 +1,10 @@
+import logging
 from typing import Optional
 
 from dvc.scm import iter_revs
 
+logger = logging.getLogger(__name__)
+
 
 def brancher(  # noqa: E302
     self,
@@ -60,6 +63,7 @@ def brancher(  # noqa: E302
 
     scm = self.scm
 
+    logger.trace("switching fs to workspace")  # type: ignore[attr-defined]
     self.fs = LocalFileSystem(url=self.root_dir)
     yield "workspace"
 
@@ -82,7 +86,9 @@ def brancher(  # noqa: E302
         from dvc.fs import GitFileSystem
 
         for sha, names in found_revs.items():
-            self._reset_cached_indecies()  # pylint: disable=W0212
+            logger.trace(  # type: ignore[attr-defined]
+                "switching fs to revision %s [%s]", sha[:7], ", ".join(names)
+            )
             self.fs = GitFileSystem(scm=scm, rev=sha)
             self.root_dir = self.fs.path.join("/", *repo_root_parts)