anchor.diff:   * `y`: yank selections
    * `p`: paste after current selection end
    * `P`: paste before current selection begin
  - * `alt-p`: paste all after current selection end, and
  + * `<a-p>`: paste all after current selection end, and
               select each pasted string.
  - * `alt-P`: paste all before current selection begin, and
  + * `<a-P>`: paste all before current selection begin, and
               select each pasted string.
    * `R`: replace current selection with yanked text
   
    * `r`: replace each character with the next entered one
   
  - * `alt-j`: join selected lines
  - * `alt-J`: join selected lines and select spaces inserted
  + * `<a-j>`: join selected lines
  + * `<a-J>`: join selected lines and select spaces inserted
               in place of line breaks
  - * `alt-m`: merge contiguous selections together (works across lines as well)
  + * `<a-m>`: merge contiguous selections together (works across lines as well)
   
    * `>`: indent selected lines
  - * `alt->`: indent selected lines, including empty lines
  + * `<a-gt>`: indent selected lines, including empty lines
    * `<`: deindent selected lines
  - * `alt-<`: deindent selected lines, do not remove incomplete
  + * `<a-lt>`: deindent selected lines, do not remove incomplete
           indent (3 leading spaces when indent is 4)
   
    * `|`: pipe each selections through the given external filter program
           and replace the selection with it's output.
  - * `alt-|`: pipe each selections through the given external filter program
  + * `<a-|>`: pipe each selections through the given external filter program
           and ignore its output
   
    * `!`: insert command output before selection
  
positive.code: using `"<reg>` prefix.
  
  `Z` will save the current selections to the register.
  `alt-Z` will append the current selections to the register.
  `z` will restore the selections from the register.
  `alt-z` will add the selections from the register to the existing ones.
  
  Jump list
  ~~~~~~~~~
  
negative.code: `s` and `S` share the search pattern with `/`, and hence entering an empty
  pattern uses the last one.
  
  As a convenience, `<a-s>` allows you to split the current selections on
  line boundaries.
  
  To clear multiple selections, use `space`. To keep only the nth selection
  use `n` followed by `space`, in order to remove a selection, use `<a-space>`.
  
  `<a-k>` allows you to enter a regex and keep only the selections that
  contains a match for this regex. using `<a-K>` you can keep the selections
  not containing a match.
  
  `C` copies the current selection to the next line (or lines if a count is given)
  `<a-C>` does the same to previous lines.
  
  `$` allows you to enter a shell command and pipe each selections to it.
  Selections whose shell command returns 0 will be kept, other will be dropped.
  