add force option for rebase to overwrite existing entities

related: openstreetmap/iD#2467

js/id/core/graph.js

@@ -112,20 +112,19 @@ iD.Graph.prototype = {
     // is used only during the history operation that merges newly downloaded
     // data into each state. To external consumers, it should appear as if the
     // graph always contained the newly downloaded data.
-    rebase: function(entities, stack) {
+    rebase: function(entities, stack, force) {
         var base = this.base(),
             i, j, k, id;
 
         for (i = 0; i < entities.length; i++) {
             var entity = entities[i];
 
-            if (base.entities[entity.id])
+            if (!force && base.entities[entity.id])
                 continue;
 
             // Merging data into the base graph
             base.entities[entity.id] = entity;
-            this._updateCalculated(undefined, entity,
-                base.parentWays, base.parentRels);
+            this._updateCalculated(undefined, entity, base.parentWays, base.parentRels);
 
             // Restore provisionally-deleted nodes that are discovered to have an extant parent
             if (entity.type === 'way') {

js/id/core/history.js

@@ -42,8 +42,8 @@ iD.History = function(context) {
         },
 
         merge: function(entities, extent) {
-            stack[0].graph.rebase(entities, _.pluck(stack, 'graph'));
-            tree.rebase(entities);
+            stack[0].graph.rebase(entities, _.pluck(stack, 'graph'), false);
+            tree.rebase(entities, false);
 
             dispatch.change(undefined, extent);
         },
@@ -237,8 +237,8 @@ iD.History = function(context) {
                     var baseEntities = h.baseEntities.map(function(entity) {
                         return iD.Entity(entity);
                     });
-                    stack[0].graph.rebase(baseEntities, _.pluck(stack, 'graph'));
-                    tree.rebase(baseEntities);
+                    stack[0].graph.rebase(baseEntities, _.pluck(stack, 'graph'), true);
+                    tree.rebase(baseEntities, true);
                 }
 
                 stack = h.stack.map(function(d) {

js/id/core/tree.js

@@ -39,13 +39,13 @@ iD.Tree = function(head) {
 
     var tree = {};
 
-    tree.rebase = function(entities) {
+    tree.rebase = function(entities, force) {
         var insertions = {};
 
         for (var i = 0; i < entities.length; i++) {
             var entity = entities[i];
 
-            if (head.entities.hasOwnProperty(entity.id) || rectangles[entity.id])
+            if (!force && (head.entities.hasOwnProperty(entity.id) || rectangles[entity.id]))
                 continue;
 
             insertions[entity.id] = entity;

js/id/id.js

@@ -56,7 +56,7 @@ window.iD = function () {
 
     connection.on('load.context', function loadContext(err, result) {
         if (altGraph) {
-            altGraph.rebase(result.data, [altGraph]);
+            altGraph.rebase(result.data, [altGraph], false);
         } else {
             history.merge(result.data, result.extent);
         }

test/spec/core/graph.js

@@ -93,6 +93,16 @@ describe('iD.Graph', function() {
             expect(graph.entity('n')).to.equal(a);
         });
 
+        it("gives precedence to new entities when force = true", function () {
+            var a = iD.Node({id: 'n'}),
+                b = iD.Node({id: 'n'}),
+                graph = iD.Graph([a]);
+
+            graph.rebase([b], [graph], true);
+
+            expect(graph.entity('n')).to.equal(b);
+        });
+
         it("inherits entities from base prototypally", function () {
             var graph = iD.Graph();