anchor.diff:  the user interface:
   
   *Default*::
  -    Default colors:::
  +    default colors:::
           The default foreground and background colors. If the value of *default*
           is used here, then the colors used will be your terminal's defaults.
   
  
positive.code: echo -markup 'default {Error}error{Default} default'
  ----
  
  Inside a markup string, a literal `{` character is written `\{`, and a literal
  backslash `\` character that precedes a `{` character is escaped as well
  (`\\`).
  
  The `{\}` string disables markup processing for the rest of the line. It
  can be used to avoid having to escape text that might be mistaken for markup
  
negative.code:             *white* *bright-black*, *bright-red*, *bright-green*,
              *bright-yellow* *bright-blue*, *bright-magenta*, *bright-cyan*,
              *bright-white*
          The color of the base face (see below):::
              *default*
          A hexadecimal value:::
              *rgb:RRGGBB*, *rgba:RRGGBBAA*
      If left unspecified, the value of *default* is used.
      Alpha values are used to blend the face onto either its base or else onto
      whatever color happens to be used at the moment. For technical reasons,
      alpha values must be >16.
  
  attributes::
      A string whose individual letters each set an attribute:
          *u*:::
              underline
          *c*:::
              curly underline
              Note: This takes precedence over underline if both are specified.
          *r*:::
              reverse
          *b*:::
              bold
          *B*:::
              blink
          *d*:::
              dim
          *i*:::
              italic
          *s*:::
              strikethrough
          *F*:::
              final::::
                  Override the previous face instead of merging with it. Can
                  only be replaced if another face with the final attribute
                  is applied.
          *f*:::
              final foreground::::
                  Same as final, but only applies to a face's foreground color.
          *g*:::
              final background::::
                  Same as final, but only applies to a face's background color.
          *a*:::
              final attributes::::
                  Same as final, but only applies to a face's attributes.
  
  base::
      The face onto which other faces apply. Its value can be any face name,
      as long as no cycle is introduced. A face can reference itself, in which
      case it'll apply on top of the version of the parent scope.
  
  == Built-in faces
  
  