Support `git` workspace directory different from `GITHUB_WORKSPACE`.

[zuckerruebe]

Hi there

When I change the locating of my git working directory to not be GITHUB_WORKSPACE any more I get the following error:

Run coverallsapp/github-action@master
  with:
    github-token: ***
    base-path: pytrnsys_gui
    path-to-lcov: test-results/coverage.lcov
    coveralls-endpoint: https://coveralls.io/
    debug: false
  env:
    PYTRNSYS_DEPENDENCY_CHANGED: false
Using lcov file: test-results/coverage.lcov
Error:  "2024-03-21T10:20:50.198Z"  'error from getOptions'
Error: Error: Command failed: git cat-file -p 0d6091d8b57ef9e37bd44fb7ed8ead3b523ee6c2
fatal: Not a valid object name 0d6091d8b57ef9e37bd44fb7ed8ead3b523ee6c2

As you can see I've tried using base-path but I imagine that's not "good enough" to specify that my git working directory is somewhere else. Is there any way to change the path to the git working directory?

Thanks