Create method history.hasChanges

js/id/graph/history.js

@@ -109,6 +109,12 @@ iD.History = function() {
             };
         },
 
+        hasChanges: function() {
+            return !!d3.sum(d3.values(this.changes()).map(function(c) {
+                return c.length;
+            }));;
+        },
+
         imagery_used: function(source) {
             if (source) imagery_used = source;
             else return _.without(

test/spec/graph/history.js

@@ -126,6 +126,18 @@ describe("iD.History", function () {
         });
     });
 
+    describe("#hasChanges", function() {
+        it("is true when any of change's values are nonempty", function() {
+            var node = iD.Node();
+            history.perform(function (graph) { return graph.replace(node); });
+            expect(history.hasChanges()).to.eql(true);
+        });
+
+        it("is false when any of change's values are empty", function() {
+            expect(history.hasChanges()).to.eql(false);
+        });
+    });
+
     describe("#reset", function () {
         it("clears the version stack", function () {
             history.perform(action, "annotation");