merge duplicate .markdown-body rules

github-markdown.css

@@ -2,6 +2,13 @@
   font-family: sans-serif;
   -ms-text-size-adjust: 100%;
   -webkit-text-size-adjust: 100%;
+  font: 13px Helvetica, arial, freesans, clean, sans-serif;
+  line-height: 1.4;
+  color: #333333;
+  font-size: 15px;
+  line-height: 1.7;
+  overflow: hidden;
+  word-wrap: break-word;
 }
 
 .markdown-body a {
@@ -52,15 +59,6 @@
   padding: 0;
 }
 
-.markdown-body {
-  font: 13px Helvetica, arial, freesans, clean, sans-serif;
-  line-height: 1.4;
-}
-
-.markdown-body {
-  color: #333333;
-}
-
 .markdown-body * {
   -moz-box-sizing: border-box;
   box-sizing: border-box;
@@ -164,13 +162,6 @@
   margin-bottom: 0;
 }
 
-.markdown-body {
-  font-size: 15px;
-  line-height: 1.7;
-  overflow: hidden;
-  word-wrap: break-word;
-}
-
 .markdown-body>*:first-child {
   margin-top: 0 !important;
 }

index.js

@@ -40,6 +40,7 @@ function getRenderedFixture(cb) {
 function cleanupCss(str) {
 	var css = require('css');
 	var style = css.parse(str);
+	var mdBodyProps = [];
 
 	style.stylesheet.rules = style.stylesheet.rules.filter(function (el) {
 		if (el.type === 'keyframes' || el.type === 'comment') {
@@ -60,10 +61,6 @@ function cleanupCss(str) {
 			});
 		}
 
-		if (el.declarations.length === 0) {
-			return false;
-		}
-
 		el.selectors = el.selectors.map(function (selector) {
 			if (/^(?:body|html)$/.test(selector)) {
 				selector = '.markdown-body';
@@ -76,9 +73,26 @@ function cleanupCss(str) {
 			return selector;
 		});
 
+		if (el.declarations.length === 0) {
+			return false;
+		}
+
+		// collect `.markdown-body` rules
+		if (el.selectors.length === 1 && el.selectors[0] === '.markdown-body') {
+			[].push.apply(mdBodyProps, el.declarations);
+			return false;
+		}
+
 		return true;
 	});
 
+	// merge `.markdown-body` rules
+	style.stylesheet.rules.unshift({
+		type: 'rule',
+		selectors: ['.markdown-body'],
+		declarations: mdBodyProps
+	});
+
 	return css.stringify(style);
 }