define-alternatives can be used to define
generic commands. These are interactive functions whose
implementation can be selected from several alternatives, as a matter
of user preference.
Define the new command command, a symbol.
When a user runs M-x command RET for the first time, Emacs prompts for which real form of the command to use, and records the selection by way of a custom variable. Using a prefix argument repeats this process of choosing an alternative.
command-alternatives should contain an alist
with alternative implementations of command.
Until this variable is set,
define-alternatives has no effect.
If customizations is non-
nil, it should consist of
defcustom keywords (typically
:version) and values to add to the declaration of