Wave 1 task core-hashing-keys: the crate's declared one-way door,
implemented byte-exact to ADR-002.
- src/hashing.rs: Algorithm (exactly GitBlobSha256 canonical /
GitBlobSha1 tolerated; BLAKE3 absent), Digest (known-length
derivation H("blob <len>\0" + content) as primary constructor;
from_git_oid_hex interop constructor, lowercase-only acceptance),
and the hashing::registry constants (0x01/0x02, 0x00 reserved; new
algorithm = new ADR)
- src/keys.rs: typed Key wrapper; as_bytes/from_bytes are the only
backend-boundary conversions; 1 algorithm byte + digest bytes
(33/21 total); rejects-never-guesses validation -> Error::KeyInvalid
- tests/git_interop.rs: the load-bearing test — byte-exact derivation
against the `git hash-object` CLI, both algorithms, small and
75-KiB content; external-oid round-trip into pool keys; both oid
formats coexisting in one flat pool
- named design point (oid hex policy): lowercase-only acceptance,
recorded in the task Notes and on from_git_oid_hex
Verified: cargo test (15 passed), cargo clippy --all-targets -- -D
warnings, cargo fmt --check, cargo test --all-features — all green.