function diff(Prism) {
  ;(function (Prism) {
    Prism.languages.diff = {
      coord: [
        // Match all kinds of coord lines (prefixed by "+++", "---" or "***").
        /^(?:\*{3}|-{3}|\+{3}).*$/m, // Match "@@ ... @@" coord lines in unified diff.
        /^@@.*@@$/m, // Match coord lines in normal diff (starts with a number).
        /^\d.*$/m
      ] // deleted, inserted, unchanged, diff
    }
    /**
     * A map from the name of a block to its line prefix.
     *
     * @type {Object<string, string>}
     */
    var PREFIXES = {
      'deleted-sign': '-',
      'deleted-arrow': '<',
      'inserted-sign': '+',
      'inserted-arrow': '>',
      unchanged: ' ',
      diff: '!'
    } // add a token for each prefix
    Object.keys(PREFIXES).forEach(function (name) {
      var prefix = PREFIXES[name]
      var alias = []
      if (!/^\w+$/.test(name)) {
        // "deleted-sign" -> "deleted"
        alias.push(/\w+/.exec(name)[0])
      }
      if (name === 'diff') {
        alias.push('bold')
      }
      Prism.languages.diff[name] = {
        pattern: RegExp(
          '^(?:[' + prefix + '].*(?:\r\n?|\n|(?![\\s\\S])))+',
          'm'
        ),
        alias: alias,
        inside: {
          line: {
            pattern: /(.)(?=[\s\S]).*(?:\r\n?|\n)?/,
            lookbehind: true
          },
          prefix: {
            pattern: /[\s\S]/,
            alias: /\w+/.exec(name)[0]
          }
        }
      }
    }) // make prefixes available to Diff plugin
    Object.defineProperty(Prism.languages.diff, 'PREFIXES', {
      value: PREFIXES
    })
  })(Prism)
}
A map from the name of a block to its line prefix.

@type {Object<string, string>}