code: function h_like_gh_other(hash) {
      // TODO: four exceptions are snih, muh, nah and dṛh
      var vowel_before_Q = hash.stem.slice(-1);
      var short_vowel = Const.longshort[vowel_before_Q];
      var re = new RegExp(vowel_before_Q + '$');
      var short_stem = hash.stem.replace(re, short_vowel);
      short_stem = [short_stem, 'ह्'].join('');
      var stem = [hash.stem, 'ह्'].join('');
      if (stem == hash.stem && short_stem == hash.stem) return;
      hash.stems = _.uniq([stem, short_stem]);
      if (debug) log('mod: h_like_gh_other', stem);
  }
docs: three things: 1) changes t, th, and dh — if they follow the h — into ḍh, 2) lengthens the vowel in front of it, if possible, 3) disappears