Keep

Keep — a commit log for a file.

The truth is an append-only log of commits, each an atomic set of typed actions. The current state is the fold of the log; a checkpoint caches that fold as of some commit. Reverting a commit appends a mark rather than erasing anything, so the log only ever grows and every state is reachable.

The log is a C0DATA stream-mode file: one ETB-committed block per commit, so a crash mid-append leaves a torn tail that readers skip and the next writer truncates. Keep knows commits, actions, revert marks, locking and versions; the application supplies the action vocabulary and the fold.