Settings are now merged a la Sublime, which is much better for migrations.

config/menus.json

@@ -33,11 +33,18 @@
   {
     "label": "Settings",
     "sub": [
-      { "label": "User Settings", "command": "session:open-settings-file", "argument": "user" },
+      { "label": "User Preferences", "command": "session:open-settings-file", "argument": "user" },
       { "label": "Keyboard", "command": "session:open-settings-file", "argument": "keys" },
       { "label": "Menus", "command": "session:open-settings-file", "argument": "menus" },
       "divider",
-      { "label": "Reset to Default",
+      { "label": "View Defaults",
+        "sub": [
+          { "label": "User Preferences", "command": "session:open-settings-defaults", "argument": "user" },
+          { "label": "Keyboard", "command": "session:open-settings-defaults", "argument": "keys" },
+          { "label": "Menus", "command": "session:open-settings-defaults", "argument": "menus" }
+        ]
+      },
+      { "label": "Reset",
         "sub": [
           { "label": "User Settings", "command": "settings:delete-local", "argument": "user" },
           { "label": "Keyboard", "command": "settings:delete-local", "argument": "keys" },

config/user.json

@@ -5,13 +5,18 @@ these files from the menu, then save it, it'll be dropped into Chrome's
 synchronized storage, which means that (theoretically) all your computers will
 get a copy. Comments are allowed, obviously--they'll be stripped out on load.
 
-Unfortunately, it's not (yet) possible to merge configuration the way that
-Sublime does, which means that this won't behave exactly like you may expect.
-If new options are introduced, you'll need to copy your settings to a new
-file, reset Caret's config to the defaults from the menu, then copy your
-configuration changes back over. Sorry about that. I'm working on it.
+Your individual settings are shallow-merged with a copy of the defaults 
+(available from Settings > View Defaults). When you first open them, your
+configuration will be a copy of the defaults, but I recommend stripping out
+anything you don't want to set explicitly, so that you can benefit if the
+default settings change in future releases.
+
+If your local file is not valid JSON, the defaults will be used. If your changes
+aren't being accepted, run the file (sans comments) through a JSON checker and
+make sure you don't have any syntax errors.
 
 */
+
 {
   //This should be any of the supported Ace themes
   "defaultTheme": "chrome", //AKA "Native"
@@ -27,4 +32,5 @@ configuration changes back over. Sorry about that. I'm working on it.
   //Web workers are used for code hinting in PHP, JavaScript, and JSON.
   //We don't yet have a way to set the worker options, but you can disable it.
   "useWorker": true
+  
 }

js/sessions.js

@@ -159,6 +159,7 @@ define([
       }
       tab.syntaxMode = syntaxValue;
     }
+    tab.setMode("ace/mode/" + syntaxValue);
     syntax.value = syntaxValue;
   };
   
@@ -385,6 +386,17 @@ define([
     });
   });
   
+  //defaults don't get loaded as files, just as content
+  command.on("session:open-settings-defaults", function(name) {
+    Settings.load(name, function() {
+      var tab = addTab(Settings.getAsString(name, true));
+      tab.syntaxMode = "javascript";
+      setTabSyntax(tab);
+      tab.fileName = name + ".json";
+      renderTabs();
+    });
+  });
+  
   command.on("session:open-launch", openFromLaunchData);
   
   var locationMemory = null;

js/settings.js

@@ -36,18 +36,61 @@ define(["command"], function(command) {
     },
     retain: function() { return false; }
   };
+  
+  var clone = function(item) {
+    var cloneArray = function(a) {
+      var n = [];
+      for (var i = 0; i < a.length; i++) {
+        if (a[i] instanceof Array) {
+          n[i] = cloneArray(a[i]);
+        } else if (typeof a[i] == "object") {
+          n[i] = cloneObject(a[i]);
+        } else {
+          n[i] = a[i];
+        }
+      }
+      return n;
+    };
+    var cloneObject = function(o) {
+      var n = {};
+      for (var key in o) {
+        if (o[key] instanceof Array) {
+          n[key] = cloneArray(o[key]);
+        } else if (typeof o[key] == "object") {
+          n[key] = cloneObject(o[key]);
+        } else {
+          n[key] = o[key];
+        }
+      }
+      return n;
+    };
+    if (item instanceof Array) {
+      return cloneArray(item);
+    }
+    return cloneObject(item);
+  };
 
   var Settings = {
     get: function(name) {
       name = name + ".json";
+      var comments = /\/\*[\s\S]*?\*\/|\/\/.*$/gm;
+      var original = clone(JSON.parse(defaults[name].replace(comments, "")));
+      var custom = {};
       try {
-        return JSON.parse(local[name].replace(/\/\*[\s\S]*?\*\/|\/\/.*$/gm, ""));
+        custom = JSON.parse(local[name].replace(comments, ""));
       } catch (e) {
-        return JSON.parse(defaults[name].replace(/\/\*[\s\S]*?\*\/|\/\/.*$/gm, ""));
+        //parse failed
       }
+      for (var key in custom) {
+        original[key] = custom[key];
+      }
+      return original;
     },
-    getAsString: function(name) {
+    getAsString: function(name, original) {
       name = name + ".json";
+      if (original) {
+        return defaults[name];
+      }
       return local[name] || defaults[name];
     },
     getAsFile: function(name) {