resolve_rev: raise DvcException on empty repo.

dvc/repo/data.py

@@ -279,9 +279,7 @@ def _transform_git_paths_to_dvc(repo: "Repo", files: Iterable[str]):
 
 
 def status(repo: "Repo", untracked_files: str = "no", **kwargs: Any) -> Status:
-    from scmrepo.exceptions import SCMError
-
-    from dvc.scm import NoSCMError
+    from dvc.scm import NoSCMError, SCMError
 
     head = kwargs.pop("head", "HEAD")
     uncommitted_diff = _diff_index_to_wtree(repo, **kwargs)

dvc/scm.py

@@ -160,7 +160,7 @@ def resolve_rev(scm: "Git", rev: str) -> str:
     except InternalRevError as exc:
         # `scm` will only resolve git branch and tag names,
         # if rev is not a sha it may be an abbreviated experiment name
-        if not rev.startswith("refs/"):
+        if not (rev == "HEAD" or rev.startswith("refs/")):
             from dvc.repo.experiments.utils import (
                 AmbiguousExpRefInfo,
                 resolve_name,

tests/unit/test_scm.py

@@ -0,0 +1,9 @@
+import pytest
+
+from dvc.exceptions import DvcException
+from dvc.scm import resolve_rev
+
+
+def test_resolve_rev_empty_git_repo(scm):
+    with pytest.raises(DvcException):
+        resolve_rev(scm, "HEAD")