1 Transient commands
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  Taking inspiration from prefix keys and prefix arguments, Transient
  implements a similar abstraction involving a prefix command, infix
  arguments and suffix commands.  We could call this abstraction a
  "transient command", but because it always involves at least two
  commands (a prefix and a suffix) we prefer to call it just a
  "transient".

        Transient keymaps are a feature provided by Emacs.
        Transients as implemented by this package involve the use
        of transient keymaps.

        Emacs provides a feature that it calls "prefix commands".
        When we talk about "prefix commands" in Transient's
        documentation, then we mean our own kind of "prefix
        commands", unless specified otherwise.  To avoid ambiguity
        we sometimes use the terms "transient prefix command" for
        our kind and "regular prefix command" for Emacs' kind.

  When the user calls a transient prefix command, then a transient
  (temporary) keymap is activated, which binds the transient's infix and
  suffix commands, and functions that control the transient state are
  added to `pre-command-hook' and `post-command-hook'.  The available
  suffix and infix commands and their state are shown in a popup buffer
  until the transient is exited by invoking a suffix command.

  Calling an infix command causes its value to be changed.  How that is
  done depends on the type of the infix command.  The simplest case is
  an infix command that represents a command-line argument that does not
  take a value.  Invoking such an infix command causes the switch to be
  toggled on or off.  More complex infix commands may read a value from
  the user, using the minibuffer.

  Calling a suffix command usually causes the transient to be exited;
  the transient keymaps and hook functions are removed, the popup buffer
  no longer shows information about the (no longer bound) suffix
  commands, the values of some public global variables are set, while
  some internal global variables are unset, and finally the command is
  actually called.  Suffix commands can also be configured to not exit
  the transient.

  A suffix command can, but does not have to, use the infix arguments in
  much the same way it can choose to use or ignore the prefix arguments.
  For a suffix command that was invoked from a transient the variable
  `transient-current-suffixes' and the function `transient-args' serve
  about the same purpose as the variables `prefix-arg' and
  `current-prefix-arg' do for any command that was called after the
  prefix arguments have been set using a command such as
  `universal-argument'.

  <http://readme.emacsair.me/transient.png>
