Add method contentLink as deprecated for plugin API

lib/api/deprecate.js

@@ -1,4 +1,5 @@
 var is = require('is');
+var objectPath = require('object-path');
 
 var logged = {};
 var disabled = {};
@@ -96,8 +97,27 @@ function disableDeprecation(key) {
     disabled[key] = true;
 }
 
+/**
+    Deprecate a method in favor of another one
+
+    @param {Book} book
+    @param {String} key
+    @param {Object} instance
+    @param {String} oldName
+    @param {String} newName
+*/
+function deprecateRenamedMethod(book, key, instance, oldName, newName, msg) {
+    msg = msg || ('"' + oldName + '" is deprecated, use "' + newName + '()" instead');
+    var fn = objectPath.get(instance, newName);
+
+    instance[oldName] = deprecateMethod(book, key, function() {
+        return fn.apply(instance, arguments);
+    }. msg);
+}
+
 module.exports = {
     method: deprecateMethod,
+    renamedMethod: deprecateRenamedMethod,
     field: deprecateField,
     enable: enableDeprecation,
     disable: disableDeprecation

lib/api/encodeGlobal.js

@@ -47,15 +47,6 @@ function encodeGlobal(output) {
             return book.isLanguageBook();
         },
 
-        /**
-            Same as isLanguageBook
-
-            @deprecated
-        */
-        isSubBook: deprecate.method(output, 'this.isSubBook', function() {
-            return book.isLanguageBook();
-        }, '"isSubBook" is deprecated, use "isLanguageBook()" instead'),
-
         /**
             Read a file from the book
 
@@ -141,6 +132,9 @@ function encodeGlobal(output) {
 
     // Deprecated properties
 
+    deprecate.renamedMethod(output, 'this.isSubBook', result, 'isSubBook', 'isLanguageBook');
+    deprecate.renamedMethod(output, 'this.contentLink', result, 'contentLink', 'output.toURL');
+
     deprecate.field(output, 'this.generator', result, 'generator',
         output.getGenerator(), '"this.generator" property is deprecated, use "this.output.name" instead');