anchor.diff:   * +nameclient <name>+: set current client name
    * +namebuf <name>+: set current buffer name
    * +echo <text>+: show <text> in status line
  - * +name <name>+: sets current client name to name
    * +nop+: does nothing, but as with every other commands, arguments may be
         evaluated. So nop can be used for example to execute a shell command
         while being sure that it's output will not be interpreted by kak.
  
positive.code:      cases where the selections may get merged.
   * +-buffer <names>+: execute in the context of each buffers in the
       comma separated list <names>
  
  The execution stops when the last key/command is reached, or an error
  is raised.
  
negative.code: Some parameters provide a way to change the context of execution:
  
   * +-client <name>+: execute in the context of the client named <name>
   * +-try-client <name>+: execute in the context of the client named
       <name> if such client exists, or else in the current context.
   * +-draft+: execute in a copy of the context of the selected client
       modifications to the selections or input state will not affect
       the client. This permits to make some modification to the buffer
  