The COW version-control surface (fork, branches, checkout, commit,
getHistory/streamHistory, asOfCommit, brain.versions) is gone, along with
its subsystems: src/versioning/, the COW object store (CommitLog,
CommitObject, RefManager, TreeObject), HistoricalStorageAdapter, and the
TypeAwareHNSWIndex path it kept alive. The Db API (now/transact/asOf/
with/persist/restore) is the one versioning model in 8.0.
Survivors and replacements:
- BlobStorage survives (the VFS stores file content through it), relocated
to src/storage/blobStorage.ts with binaryDataCodec.ts; its adapter
interface is now BlobStoreAdapter, slimmed to the consumed surface
(write/read/has/delete/getMetadata + MIME-aware compression policy).
- brain.migrate() backup branches are replaced by persist-before-migrate:
MigrateOptions.backupTo persists a hard-link snapshot of the current
generation before any transform runs; MigrationResult.backupPath reports
it, and brain.restore(path) brings it back wholesale.
- CLI: cow.ts (fork/branch/checkout/history/migrate) is replaced by
snapshot.ts — snapshot <path>, restore <path>, history (tx-log),
generation.
- New public read API: brain.transactionLog({limit}) exposes the reified
tx-log (generation/timestamp/meta, newest first) that backs the CLI
history command; TxLogEntry is exported.
Tests: superseded suites deleted; fork/commit blocks excised from shared
suites; BlobStorage tests relocated + reworked against the slimmed store;
migration tests now prove the backupTo snapshot/restore round trip; new
transactionLog coverage in db-mvcc.
BlobStorage.write() in `auto` compression mode now consults the new
`BlobWriteOptions.mimeType` and skips zstd for MIME types known to be
already heavily compressed — JPEG, PNG, WebP, MP4, WebM, MP3, ZIP, PDF,
Office formats, etc. Gzip/zstd over these formats wastes CPU for no
measurable byte savings; the payload entropy is already near maximal,
so the output is the same size or slightly larger plus the cost of
running the compressor.
The denylist `ALREADY_COMPRESSED_MIME_TYPES` is a conservative set of
well-known formats. False negatives (compressing something we should
have skipped) waste CPU; false positives (skipping something we could
have compressed) waste a few percent of bytes. The denylist favours
CPU-cycle safety because the formats listed here are the ones where
gzip/zstd is reliably a net loss.
The policy applies only to `auto` mode. Explicit `'zstd'` and `'none'`
are honoured because the caller is asserting the choice. The new
`isAlreadyCompressedMimeType()` is exported for consumers that want to
make the same decision before calling `write()`.
VFS / consumer wiring (pass mimeType from VFS through to BlobStorage)
is part of the 2.5.0 #27 storage unification work — when that lands,
every media upload through VFS will engage this policy automatically.
For now consumers opt-in by passing `mimeType` in BlobWriteOptions.
Tests (1447 total, +10):
- isAlreadyCompressedMimeType helper: canonical types, case-insensitive
+ parameter stripping, false-on-missing.
- write() auto-mode: image/jpeg + video/mp4 + application/zip all skip
compression (metadata.compression === 'none'); text/plain is allowed
through to zstd (either 'zstd' or 'none' depending on optional dep).
- Read decompresses transparently regardless of write-side decision.
- Explicit compression options bypass the policy.
