Fixes: https://github.com/go-gitea/gitea/issues/38818
Accepts GitHub's `$/` self-repository prefix in a reusable workflow
`uses:`, alongside `./`.
Gitea's `./` already resolves against the caller's own source repo and
commit, which is what `$/` means, so the two are aliases here. Cycle
detection folds both prefixes onto one key.
Related PR for step-level support:
https://gitea.com/gitea/runner/pulls/1150
silverwindandGitHub
4c382cea59