console.diff with single argument behaves like console.diffPush

Author: zendive

README.md

@@ -10,7 +10,7 @@ Example
 console.diff(left, right);
 console.diffLeft(left);
 console.diffRight(right);
-console.diffPush(next);
+console.diffPush(next); // private case of console.diff with single argument
 ```
 ![screenshot](./doc/screenshot.png)
 

src/js/jsdiff-devtools.js

@@ -57,7 +57,12 @@ function jsdiff_devtools_extension_api() {
 
   Object.assign(console, {
     diff(left, right) {
-      w.postMessage({payload: {left, right}, source}, '*');
+      if (right === undefined) {
+        w.postMessage({payload: {push: left}, source}, '*');
+      }
+      else {
+        w.postMessage({payload: {left, right}, source}, '*');
+      }
     },
     diffLeft(left) {
       w.postMessage({payload: {left}, source}, '*');