Describe the bug

darker...................................................................Failed
- hook id: darker
- exit code: 123

ERROR:darkgraylib.git:fatal: bad revision 'HEAD'

To Reproduce
Steps to reproduce the behavior:

1. mkdir test-darker && cd test-darker
2. git init
3. add .pre-commit-config.yaml with darker configured
4. git add . && git commt -m 'will fail when the first commit'

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add copy/paste the output or attach a screenshots to help explain your problem.

Environment (please complete the following information):

1. pre-commit==4.2.0
2. darker==2.1.1
3. black==25.1.0

Additional context
Add any other context about the problem here.