UNDO — putting a run back

Raised by lemonfiber undo, and UNDO-3 also by any command that made a change and could not record it. A run of changes goes back whole or not at all, so every refusal undo makes comes before anything is reversed rather than part-way through.

Code	Severity	Exit	What it means	What to do
UNDO-1	error	1	No run in the record carries the stamp you asked for. It may have fallen outside the horizon the record keeps, or the stamp may be mistyped. Nothing was put back.	Run lemonfiber history and take the stamp from the entry you want.
UNDO-2	error	1	The stamp names more than one run, and putting back the wrong one is not something to guess at. Nothing was put back.	The message names each run the stamp covers; ask for one of them once the surfaces carry it.
UNDO-3	error	1	One change in the run cannot be reversed, and a run goes back whole or not at all — so nothing was put back. The message names the change and why it will not go. Raised by a command that made a change, it means the change was made and could not be written to the change journal: the change stands, and cannot be put back, because a reversal reads the journal.	Deal with that change first, or restore from a backup. Where a change could not be recorded, check that lemonfiber's configuration directory can be written and has space.
UNDO-4	error	1	This run has nowhere it knows to look for what was changed. What lemonfiber changed is recorded in its own directory, and this machine would not say where that is. Nothing was put back.	Set a home directory for this user and run it again.

What each severity and each exit means is on every error by code, beside every other family.