Function: winner-mode

Toggle Winner mode on or off.
With a prefix argument ARG, enable Winner mode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
the mode if ARG is omitted or nil, and toggle it if ARG is `toggle'.
key binding
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C-c Prefix Command

C-c winner-undo C-c winner-redo

Variable: winner-mode

Non-nil if Winner mode is enabled.
See the command `winner-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `winner-mode'.