Add a check for InvalidGitRepositoryError in get_repo_id function

[slimreaper35]

https://github.com/containerbuildsystem/cachi2/blob/main/cachi2/core/scm.py#L37

Currently, we are not checking if a directory is initialized as a git repository. If it is not, repo = Repo(repo) will result in an ugly exception. We should handle it properly as we do when checking if the repo has set an origin remote.

To reproduce:

git clone [email protected]:cachito-testing/cachi2-pip-extra.git
cd cachi2-pip-extra
git switch no-metadata
rm -rf .git/
cachi2 fetch-deps --source . pip