Revert

Undo the edits a run made: its fs.write, fs.edit and fs.apply_bundle calls, named by their call_id. Every file they changed goes back to what it held before the first of them, in one journaled bundle, so either every file is restored or none is.

An undo is bound to what the edits left. A file that changed after them is refused, naming it, and nothing is restored: read what changed and decide what to keep before undoing again. A file the edits created is deleted; a file they deleted comes back.

This is an ordinary run with its own receipt, so an undo is as governed as the edit it undoes.