Add doc comments to the common file util. [ci skip]

lib/common/file.js

@@ -9,10 +9,26 @@ var minify = require('../common/minify.js');
 
 /*----------------------------------------------------------------------------*/
 
+/**
+ * Creates a [fs.copy](https://github.com/jprichardson/node-fs-extra#copy)
+ * function with `srcPath` and `destPath` partially applied.
+ *
+ * @memberOf file
+ * @param {string} srcPath The path of the file to copy.
+ * @param {string} destPath The path to copy the file to.
+ * @returns {Function} Returns the partially applied function.
+ */
 function copy(srcPath, destPath) {
   return _.partial(fs.copy, srcPath, destPath);
 }
 
+/**
+ * Creates an object of compiled template and base name pairs that match `pattern`.
+ *
+ * @memberOf file
+ * @param {string} pattern The glob pattern to be match.
+ * @returns {Object} Returns the object of compiled templates.
+ */
 function globTemplate(pattern) {
   return _.transform(glob.sync(pattern), function(result, filePath) {
     var key = path.basename(filePath, path.extname(filePath));
@@ -20,14 +36,33 @@ function globTemplate(pattern) {
   }, {});
 }
 
+/**
+ * Creates a `minify` function with `srcPath` and `destPath` partially applied.
+ *
+ * @memberOf file
+ * @param {string} srcPath The path of the file to minify.
+ * @param {string} destPath The path to write the file to.
+ * @returns {Function} Returns the partially applied function.
+ */
 function min(srcPath, destPath) {
   return _.partial(minify, srcPath, destPath);
 }
 
-function write(filePath, data) {
-  return _.partial(fs.writeFile, filePath, data);
+/**
+ * Creates a [fs.writeFile](https://nodejs.org/api/fs.html#fs_fs_writefile_file_data_options_callback)
+ * function with `filePath` and `data` partially applied.
+ *
+ * @memberOf file
+ * @param {string} destPath The path to write the file to.
+ * @param {string} data The data to write to the file.
+ * @returns {Function} Returns the partially applied function.
+ */
+function write(destPath, data) {
+  return _.partial(fs.writeFile, destPath, data);
 }
 
+/*----------------------------------------------------------------------------*/
+
 module.exports = {
   'copy': copy,
   'globTemplate': globTemplate,