add some comments to the clean command module

lib/commands/clean.js

@@ -103,6 +103,13 @@ exports.clean = function (dir, opt, callback) {
 };
 
 
+/**
+ * Delete multiple directory paths.
+ *
+ * @param {Array} dirs
+ * @param {Function} callback
+ */
+
 exports.deleteDirs = function (dirs, callback) {
     async.forEach(dirs, function (d, cb) {
         utils.rm('-rf', d, cb);
@@ -111,6 +118,15 @@ exports.deleteDirs = function (dirs, callback) {
 };
 
 
+/**
+ * Discover package directories that do not form part of the current
+ * package version tree.
+ *
+ * @param {String} dir - the root package dir
+ * @param {Object} opt - the options object
+ * @param {Function} callback
+ */
+
 exports.unusedDirs = function (dir, opt, callback) {
     settings.load(dir, function (err, cfg) {
         if (err) {
@@ -134,6 +150,15 @@ exports.unusedDirs = function (dir, opt, callback) {
 };
 
 
+/**
+ * Lists packages in the package dir and compares against the provided
+ * version tree, returning the packages not in the tree.
+ *
+ * @param {Object} packages - version tree
+ * @param {Object} opt - options object
+ * @param {Function} callback
+ */
+
 exports.unusedDirsTree = function (packages, opt, callback) {
     exports.listDirs(opt.target_dir, function (err, dirs) {
         if (err) {
@@ -152,6 +177,13 @@ exports.unusedDirsTree = function (packages, opt, callback) {
 };
 
 
+/**
+ * List directories within a directory. Filters out regular files etc.
+ *
+ * @param {String} dir
+ * @param {Function} callback
+ */
+
 exports.listDirs = function (dir, callback) {
     fs.readdir(dir, function (err, files) {
         if (err) {
@@ -173,6 +205,14 @@ exports.listDirs = function (dir, callback) {
 };
 
 
+/**
+ * Checks if a path is a directory, returns an object containing the
+ * checked path and a boolean for whether it's a directory.
+ *
+ * @param {String} path
+ * @param {Function} callback
+ */
+
 exports.isDir = function (path, callback) {
     fs.stat(path, function (err, info) {
         if (err) {