Major Section: HISTORY
Examples:
:ubu :x-3 ; undo the last three commands (same as :ubt :x-2)
:ubu (:x -3) ; same as above
:ubu fn ; undo back up to, but not including the introduction of fn
; (so fn will continue to be defined)
:ubu 5 ; undo back up to, but not including, the fifth command
; executed (leaving the first five commands in place)
See command-descriptor.
Ubu takes one argument, a command descriptor, and undoes the
commands from :max (aka :x) up to, but not including, the
indicated command. See command-descriptor.
Ubu can cause errors or queries. To avoid these, see ubu!.
Also see ubt, which is similar but also undoes the indicated command. As
for :ubt, :oops will undo the undo (see oops) and
ubu will not undo into ``prehistory''.
See u for how to undo just the latest command, and see ubt and see ubt! for how to undo back through (that is, including) the current command.