=================================== FAILURES ===================================
________________ test_get_conflicted_files_with_file_named_head ________________
/home/asottile/workspace/pre-commit/tests/git_test.py:149: in test_get_conflicted_files_with_file_named_head
    ret = set(git.get_conflicted_files())
/home/asottile/workspace/pre-commit/pre_commit/git.py:127: in get_conflicted_files
    cmd_output(
/home/asottile/workspace/pre-commit/pre_commit/util.py:117: in cmd_output
    returncode, stdout_b, stderr_b = cmd_output_b(*cmd, **kwargs)
/home/asottile/workspace/pre-commit/pre_commit/util.py:111: in cmd_output_b
    raise CalledProcessError(returncode, cmd, stdout_b, stderr_b)
E   pre_commit.util.CalledProcessError: command: ('/usr/bin/git', 'diff', '--name-only', '--no-ext-diff', '-z', '-m', 'ab3e3cf46f673553f5d9ca374de5fe0d2a1989c8', 'HEAD', 'MERGE_HEAD')
E   return code: 128
E   stdout: (none)
E   stderr:
E       fatal: ambiguous argument 'HEAD': both revision and filename
E       Use '--' to separate paths from revisions, like this:
E       'git <command> [<revision>...] -- [<file>...]'
----------------------------- Captured stdout call -----------------------------
[INFO] Checking merge-conflict files only.
------------------------------ Captured log call -------------------------------
INFO     pre_commit.git:git.py:115 Checking merge-conflict files only.
=========================== short test summary info ============================
FAILED tests/git_test.py::test_get_conflicted_files_with_file_named_head - pre_commit.util.CalledProcessError: command: ('/usr/bin/git', 'diff', '--na...
================= 1 failed, 10 passed, 22 deselected in 0.56s ==================