Add contexts.withContext.

--HG--
branch : groups

common/content/commandline.js

@@ -424,10 +424,10 @@ var CommandExMode = Class("CommandExMode", CommandMode, {
     },
 
     onSubmit: function onSubmit(command) {
-        io.withSavedValues(["readHeredoc"], function () {
-            this.readHeredoc = commandline.readHeredoc;
-            contexts.withSavedValues(["context"], function () {
-                this.context = { file: "[Command Line]", line: 1 };
+        contexts.withContext({ file: "[Command Line]", line: 1 },
+                             function () {
+            io.withSavedValues(["readHeredoc"], function () {
+                this.readHeredoc = commandline.readHeredoc;
                 commands.repeat = command;
                 dactyl.execute(command);
             });

common/content/commands.js

@@ -635,10 +635,8 @@ var Commands = Module("commands", {
      *      command string.
      */
     execute: function (string, tokens, silent, args, context) {
-        contexts.withSavedValues(["context"], function () {
-            context = update({}, context || this.context || { file: "[Command Line]", line: 1 });
-            this.context = context;
-
+        contexts.withContext(context || this.context || { file: "[Command Line]", line: 1 },
+                             function (context) {
             io.withSavedValues(["readHeredoc"], function () {
                 this.readHeredoc = function (end) {
                     let res = [];

common/content/contexts.js

@@ -270,7 +270,13 @@ var Contexts = Module("contexts", {
         get default() (contexts.context && contexts.context.group || contexts.user)[name],
 
         completer: function (context) completion.group(context)
-    })
+    }),
+
+    withContext: function withContext(defaults, callback, self)
+        this.withSavedValues(["context"], function () {
+            this.context = defaults && update({}, defaults);
+            return callback.call(self, this.context);
+        })
 }, {
     Context: modules.Script = function Context(file, group, args) {
         function Const(val) Class.Property({ enumerable: true, value: val });

common/content/mow.js

@@ -90,8 +90,6 @@ var MOW = Module("mow", {
      * @param {string} highlightGroup
      */
     echo: function echo(data, highlightGroup, silent) {
-        this.document;
-        util.dump(String(this.widget), String(this.window), String(this.document));
         let body = this.document.body;
 
         this.widgets.message = null;

common/modules/io.jsm

@@ -150,8 +150,7 @@ var IO = Module("io", {
             params = params || {};
 
             let time = Date.now();
-            return contexts.withSavedValues(["context"], function _source() {
-                contexts.context = null;
+            return contexts.withContext(null, function () {
                 try {
                     var file = util.getFile(filename) || io.File(filename);