Storing secrets in a repository with non-secrets is bad, because access is pre-repo, and it would hurt your ability to limit secret access to the smallest possible audience.
Access is per-repo, so if you have enough secrets and disparate interested parties, the number of required repos could make a dedicated alternative far more manageable.
However, storing secrets in a git repo is still not as good as a purpose built store, because the access control on git is not fine grained enough.