Absolutely. Going further, the little-known git-notes [1] feature also uses its own reference namespace, `refs/notes/` Going even further, Gerrit [2] leverage

Absolutely. Going further, the little-known git-notes [1] feature also uses its own reference namespace, `refs/notes/` Going even further, Gerrit [2] leverages the wide-open reference namespace/directories to create its own. For example, pushing under the `refs/for/` namespace creates a new review, and specific reviews can be looked up under the `refs/changes/` namespace. Even even further, Gerrit's special repos All-Users.git and All-Projects.git are "databases" for project configuration and user configuration, where for example external IDs (like usernames) are stored under the special `refs/meta/external-ids` ref/branch. This has the notable benefit that all configuration changes are tracked and auditable. I believe git-appraise [3] also leverages special reference namespaces in Git for performing its review duties (but I don't know details) Edit: actually no, it "just" leverages git-notes. [1] https://git-scm.com/docs/git-notes https://git-scm.com/docs/git-notes [2] https://gerrit-review.googlesource.com/Documentation/note-db.html https://gerrit-review.googlesource.com/Documentation/note-db... [3] https://github.com/google/git-appraise https://github.com/google/git-appraise