Add methods to join paths to the destination/source root

Fix #687

lib/base.js

@@ -639,6 +639,28 @@ Base.prototype.sourceRoot = function (rootPath) {
   return this._sourceRoot;
 };
 
+/**
+ * Join a path to the source root.
+ * @param  {...String} path
+ * @return {String}    joined path
+ */
+
+Base.prototype.templatePath = function () {
+  var args = [this.sourceRoot()].concat(_.toArray(arguments));
+  return path.join.apply(path, args);
+};
+
+/**
+ * Join a path to the destination root.
+ * @param  {...String} path
+ * @return {String}    joined path
+ */
+
+Base.prototype.destinationPath = function () {
+  var args = [this.destinationRoot()].concat(_.toArray(arguments));
+  return path.join.apply(path, args);
+};
+
 /**
  * Return a file Env validation filter checking for collision
  */

test/base.js

@@ -759,6 +759,32 @@ describe('generators.Base', function () {
     });
   });
 
+  describe('#templatePath()', function () {
+    it('joins path to the source root', function () {
+      assert.equal(
+        this.dummy.templatePath('bar.js'),
+        path.join(this.dummy.sourceRoot(), 'bar.js')
+      );
+      assert.equal(
+        this.dummy.templatePath('dir/', 'bar.js'),
+        path.join(this.dummy.sourceRoot(), '/dir/bar.js')
+      );
+    });
+  });
+
+  describe('#destinationPath()', function () {
+    it('joins path to the source root', function () {
+      assert.equal(
+        this.dummy.destinationPath('bar.js'),
+        path.join(this.dummy.destinationRoot(), 'bar.js')
+      );
+      assert.equal(
+        this.dummy.destinationPath('dir/', 'bar.js'),
+        path.join(this.dummy.destinationRoot(), '/dir/bar.js')
+      );
+    });
+  });
+
   describe('Events', function () {
     before(function () {
       var Generator = this.Generator = function () {