Ref.resolve/2 handles exact full refs only. Every /tree/:ref/... URL in a hosting product needs to resolve arbitrary revision expressions.

Scope

Revision.parse_and_resolve(repo, spec) supports the documented git revision grammar:

• Full SHA and abbreviated SHA (with ambiguity detection)
• Refs by short name (main), ordered lookup (refs/heads/main, refs/tags/main)
• @ and HEAD
• X~N, X^N, X^{tree}, X^{commit}, X^{tag}, X^{}
• X@{N} (reflog — requires reflog feature #5) — optional
• X@{date} — optional
• refname:path — return blob/tree at path (used by file view URLs)

Acceptance

• Fuzz-tested against git rev-parse on a fixture repo for ≥200 expressions.
• Returns {:ok, sha, object_type} or typed error (ambiguous, not_found, invalid).