When connecting nodes, prefer to keep an existing (not new) node

(closes #4974, closes #4674)

modules/actions/connect.js

@@ -3,8 +3,8 @@ import { actionDeleteNode } from './delete_node';
 
 // Connect the ways at the given nodes.
 //
-// The last node will survive. All other nodes will be replaced with
-// the surviving node in parent ways, and then removed.
+// First choose a node to be the survivor, with preference given
+// to an existing (not new) node.
 //
 // Tags and relation memberships of of non-surviving nodes are merged
 // to the survivor.
@@ -17,11 +17,20 @@ import { actionDeleteNode } from './delete_node';
 //
 export function actionConnect(nodeIds) {
     return function(graph) {
-        var last = nodeIds[nodeIds.length - 1];
-        var survivor = graph.entity(last);
+        var survivor;
+        var node;
+        var i;
 
-        for (var i = 0; i < nodeIds.length - 1; i++) {
-            var node = graph.entity(nodeIds[i]);
+        // Choose a survivor node, prefer an existing (not new) node - #4974
+        for (i = 0; i < nodeIds.length; i++) {
+            survivor = graph.entity(nodeIds[i]);
+            if (survivor.version) break;  // found one
+        }
+
+        // Replace all non-surviving nodes with the survivor and merge tags.
+        for (i = 0; i < nodeIds.length; i++) {
+            node = graph.entity(nodeIds[i]);
+            if (node.id === survivor.id) continue;
 
             /* eslint-disable no-loop-func */
             graph.parentWays(node).forEach(function(parent) {