Change tooltip for save button depending on disabled state. Fixes #573

js/id/ui/save.js

@@ -78,10 +78,11 @@ iD.ui.Save = function(context) {
             .attr('class', 'save col12 disabled')
             .attr('tabindex', -1)
             .on('click', save)
+            .attr('data-original-title',
+                iD.ui.tooltipHtml(t('save.no_changes'), key))
             .call(bootstrap.tooltip()
                 .placement('bottom')
-                .html(true)
-                .title(iD.ui.tooltipHtml(t('save.help'), key)));
+                .html(true));
 
         button.append('span')
             .attr('class', 'label')
@@ -99,6 +100,11 @@ iD.ui.Save = function(context) {
         context.history().on('change.save', function() {
             var hasChanges = history.hasChanges();
 
+            button
+                .attr('data-original-title',
+                    iD.ui.tooltipHtml(t(hasChanges ?
+                        'save.help' : 'save.no_changes'), key));
+
             button
                 .classed('disabled', !hasChanges)
                 .classed('has-count', hasChanges);

locale/en.js

@@ -205,6 +205,7 @@ locale.en = {
     save: {
         title: "Save",
         help: "Save changes to OpenStreetMap, making them visible to other users.",
+        no_changes: "No changes to save.",
         error: "An error occurred while trying to save",
         uploading: "Uploading changes to OpenStreetMap.",
         unsaved_changes: "You have unsaved changes"