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

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

Start by tracing how coverallsapp/github-action resolves the git working directory and how base-path relates to GITHUB_WORKSPACE, then reproduce the failure with git checked out elsewhere. Done means the action can locate the repository and resolve git cat-file successfully while still uploading test-results/coverage.lcov.