plugins/moveElemsAttrsToGroup: merge split-level transforms instead of replacing (fix #10)

plugins/moveElemsAttrsToGroup.js

@@ -29,6 +29,7 @@ exports.moveElemsAttrsToGroup = function(item, params) {
     if (item.isElem('g') && !item.isEmpty() && item.content.length > 1) {
 
         var intersection = {},
+            hasTransform = false,
             every = item.content.every(function(g) {
                 if (g.elem && g.attrs) {
                     if (!Object.keys(intersection).length) {
@@ -48,8 +49,16 @@ exports.moveElemsAttrsToGroup = function(item, params) {
             item.content.forEach(function(g) {
                 for (var name in intersection) {
                     g.removeAttr(name);
+
+                    if (name === 'transform') {
+                        if (!hasTransform) {
+                            item.attr('transform').value += ' ' + intersection[name].value;
+                            hasTransform = true;
+                        }
+                    } else {
                         item.addAttr(intersection[name]);
                     }
+                }
             });
         }
 

test/plugins/moveElemsAttrsToGroup.04.orig.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+    <g transform="rotate(45)">
+        <g transform="scale(2)" attr="val">
+            <path d="..."/>
+        </g>
+        <circle attr="val" transform="scale(2)"/>
+    </g>
+</svg>

test/plugins/moveElemsAttrsToGroup.04.should.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+    <g transform="rotate(45) scale(2)" attr="val">
+        <g>
+            <path d="..."/>
+        </g>
+        <circle/>
+    </g>
+</svg>