ls: specify rev as kwarg (#6121)

Fixes #5865

dvc/repo/ls.py

@@ -28,7 +28,7 @@ def ls(url, path=None, rev=None, recursive=None, dvc_only=False):
     """
     from . import Repo
 
-    with Repo.open(url, rev, subrepos=True, uninitialized=True) as repo:
+    with Repo.open(url, rev=rev, subrepos=True, uninitialized=True) as repo:
         path_info = PathInfo(repo.root_dir)
         if path:
             path_info /= path

tests/func/test_ls.py

@@ -273,6 +273,24 @@ def test_ls_repo_with_removed_dvc_dir_with_path_file(tmp_dir, dvc, scm):
     match_files(files, ((("file",), True),))
 
 
+def test_ls_repo_with_rev(erepo_dir):
+    with erepo_dir.chdir():
+        erepo_dir.scm_gen(FS_STRUCTURE, commit="init")
+        erepo_dir.dvc_gen(DVC_STRUCTURE, commit="dvc")
+
+    rev = erepo_dir.scm.list_all_commits()[1]
+    files = Repo.ls(os.fspath(erepo_dir), rev=rev)
+    match_files(
+        files,
+        (
+            ((".dvcignore",), False),
+            ((".gitignore",), False),
+            (("README.md",), False),
+            (("model",), False),
+        ),
+    )
+
+
 def test_ls_remote_repo(erepo_dir):
     with erepo_dir.chdir():
         erepo_dir.scm_gen(FS_STRUCTURE, commit="init")