add GFM style checkbox in list. see chjj#111 for detail

lib/marked.js

@@ -149,6 +149,7 @@ Lexer.prototype.token = function(src, top) {
     , bull
     , b
     , item
+    , gtr = this.options.gfm && this.options.gfmTodoRule
     , space
     , i
     , l;
@@ -332,6 +333,14 @@ Lexer.prototype.token = function(src, top) {
             : 'list_item_start'
         });
 
+        if (gtr && (b = gtr.exec(item))) {
+            this.tokens.push({
+                type: 'text',
+                text: b[0]
+            });
+
+            item = item.substring(b[0].length);
+        }
         // Recurse.
         this.token(item, false);
 
@@ -948,6 +957,17 @@ Parser.prototype.tok = function() {
     }
     case 'list_item_start': {
       var body = '';
+      var gtr = this.options.gfm && this.options.gfmTodoRule;
+      var peek,
+          m;
+
+      if (gtr && (peek = this.peek()) && peek.type === 'text') {
+          if ((m = gtr.exec(peek.text)) && m[0].length === peek.text.length) {
+              this.next();
+              body += '<input type="checkbox" disabled' +
+                  (m[1] === ' ' ? '' : ' checked') + ' /> '
+          }
+      }
 
       while (this.next().type !== 'list_item_end') {
         body += this.token.type === 'text'
@@ -1127,6 +1147,7 @@ marked.setOptions = function(opt) {
 
 marked.defaults = {
   gfm: true,
+  gfmTodoRule: /^\[([- ovx*+%#@~?])\] +/,
   tables: true,
   breaks: false,
   pedantic: false,

test/tests/gfm_todo_list.html

@@ -0,0 +1,5 @@
+<ul>
+<li><input type="checkbox" disabled /> abc
+[ ] bcd</li>
+<li><input type="checkbox" disabled checked /> cde</li>
+</ul>

test/tests/gfm_todo_list.text

@@ -0,0 +1,3 @@
+* [ ] abc
+  [ ] bcd
+* [x] cde