dvc: drop unused params in Repo.brancher()

dvc/repo/brancher.py

@@ -5,12 +5,7 @@ from dvc.scm.tree import WorkingTree
 
 
 def brancher(  # noqa: E302
-    self,
-    branches=None,
-    all_branches=False,
-    tags=None,
-    all_tags=False,
-    all_commits=False,
+    self, all_branches=False, all_tags=False, all_commits=False
 ):
     """Generator that iterates over specified revisions.
 
@@ -26,7 +21,7 @@ def brancher(  # noqa: E302
             - empty string it there is no branches to iterate over
             - "Working Tree" if there are uncommitted changes in the SCM repo
     """
-    if not any([branches, all_branches, tags, all_tags, all_commits]):
+    if not any([all_branches, all_tags, all_commits]):
         yield ""
         return
 
@@ -42,16 +37,10 @@ def brancher(  # noqa: E302
         revs = scm.list_all_commits()
     else:
         if all_branches:
-            branches = scm.list_branches()
+            revs.extend(scm.list_branches())
 
         if all_tags:
-            tags = scm.list_tags()
-
-        if branches is not None:
-            revs.extend(branches)
-
-        if tags is not None:
-            revs.extend(tags)
+            revs.extend(scm.list_tags())
 
     # NOTE: it might be a good idea to wrap this loop in try/finally block
     # to don't leave the tree on some unexpected branch after the