Repo Indexer: improved error logging (#620)
Repo Indexer: improved error logging (#620)

* initial functionality for repo-tracking

* proto to yaml; waitgroups to semaphores; various comments addressed

* remove unsupported named&numbered capturing group

* changed version regex to optional; tag versioning is the default and is always done;

* improved error logging in preparation stage
google/osv.dev,google/osv.dev,google/osv.dev,google/osv.dev,google/osv.dev