test.js

    // Helper Functions:
    // responder - returns a function that takes arguments to close over and returns
    // a function bound to `this`.
    var responder = function(fn) {
        return function() {
            var closed = [].slice.call(arguments);
            return function() {
                return fn.apply(this, closed.concat([].slice.call(arguments)));
            }.bind(this);
        };
    };

    // emitterize - turn a normal `fs.something(callback)` function into one that returns
    // an `EventEmitter`.
    var EventEmitter = require('events').EventEmitter;
    var emitterize = function(fn) {
        return function() {
            var ee = new EventEmitter();
            fn.apply({}, [].call(arguments).concat([function(err, data) {
                if(err) ee.emit('error', err);
                else ee.emit('data', data);
            }]));
            return ee;
        };
    };

    // The meat of the validator code:
    var fs = require('fs');
    var path = require('path');
    var stat = emitterize(fs.stat);
    var readFile = emitterize(fs.readFile);

    var RepoPathValidator = function(basePath) {
        EventEmitter.call(this);

        this.basePath = path.join(basePath, '.git');
        this.objectsPath = path.join(this.basePath, 'objects');
        this.indexFilePath = path.join(this.basePath, 'index');
        this.headFilePath = path.join(this.basePath, 'HEAD');

        stat(this.basePath).
            on('data', this.baseDirOkay()).
            on('error', this.emit.bind(this, 'error'));
    };

    RepoPathValidator.prototype = new EventEmitter();

    RepoPathValidator.prototype.baseDirOkay = responder(function(stats) {
        if(!stats.isDirectory())
            this.emit('error', 'Not a repo');
        else
            stat(this.objectsPath).
                on('data', this.objectDirOkay()).
                on('error', this.emit.bind(this, 'error'));
    });

    RepoPathValidator.prototype.objectDirOkay = responder(function(stats) {
        if(!stats.isDirectory())
            this.emit('error', 'Not a repo');
        else
            readFile(this.indexFilePath).
                on('data', this.indexFileOkay()).
                on('error', this.emit.bind(this, 'error'));
    });

    RepoPathValidator.prototype.indexFileOkay = responder(function(data) {
        this.indexData = data;
        readFile(this.headFilePath).
            on('data', this.headFileOkay()).
            on('error', this.emit.bind(this, 'error'));
    });

    RepoPathValidator.prototype.headFileOkay = responder(function(data) {
        this.headData = data;
        this.emit('data', this);
    });