node-sass: node-sass --watch doesn't work for directories

I noticed that the --watch command line switch added by #147 isn’t documented in README.md, so I was going to fork and add it, but shortly realized that --watch doesn’t actually seem to work. A couple issues here:

First of all, I imagine that node-sass --watch should work without specifying an input file, like the SASS Ruby gem. However, it doesn’t appear to work that way:

peterjmag@peterjmags-iMac ~/node/node-sass-watch 
$ node-sass --watch scss/
Compile .scss files with node-sass.
Usage: node-sass [options] <input.scss> [<output.css>]

Options:
[...]

Argument check failed: function (argv){
    if (argv.help) { return true; }
    if (argv._.length < 1) { return false; }
  }
peterjmag@peterjmags-iMac ~/node/node-sass-watch 
$ node-sass --watch=scss/
Compile .scss files with node-sass.
Usage: node-sass [options] <input.scss> [<output.css>]

Options:
[...]

Argument check failed: function (argv){
    if (argv.help) { return true; }
    if (argv._.length < 1) { return false; }
  }

If I then add an input file argument (a dummy file for instance, just to satisfy the requirement), I get the following:

peterjmag@peterjmags-iMac ~/node/node-sass-watch 
$ ls scss/
test.scss  test2.scss
peterjmag@peterjmags-iMac ~/node/node-sass-watch 
$ node-sass scss/ --watch=scss/
error reading file "scss/"

peterjmag@peterjmags-iMac ~/node/node-sass-watch 
$ node-sass scss/test.scss --watch=scss/
Rendering Complete, saving .css file...
Wrote CSS to /Users/admin/node/node-sass-watch/test.css
[saved a minor change to test2.scss, which triggers the following]
NaN
Rendering Complete, saving .css file...
Wrote CSS to /Users/admin/node/node-sass-watch/test.css
[saved test2.scss again]
NaN
Rendering Complete, saving .css file...
Wrote CSS to /Users/admin/node/node-sass-watch/test.css

It’s also entirely possible that I’m missing something obvious here, so let me know if that’s the case. Either way, I’m happy to update the docs once this is resolved! 😃