enable github installs

Author: ngokevin

README.md

@@ -33,6 +33,24 @@ Create a JSON spec of packages to be installed, e.g. at `test/multidep.json`:
 
 Do not use fuzzy versions (`"^0.16.0"`) - this will cause problems.
 
+#### Installing the packages from GitHub
+
+To specify a package from GitHub, specify an array where the first value points
+to a GitHub repository (optionally with branch or tag), and the second value
+will be suffixed to the install path. This will install the `somebranch` branch
+of the `username/brocolli` repository to `test/multidep_modules/brocolli-thatbranch`:
+
+```json
+{
+  "path": "test/multidep_modules",
+  "versions": {
+    "broccoli": [["username/brocolli#somebranch", "thatbranch"]]
+  }
+}
+```
+
+This is currently only for installing, does not work with requiring.
+
 ### Installing the packages from npm
 
 Next, run

index.js

@@ -72,14 +72,29 @@ module.exports.install = function(specPath) {
   Object.keys(spec.versions).sort().forEach(function(packageName) {
     spec.versions[packageName].forEach(function(version) {
       promise = promise.then(function() {
-        var packagePath = path.join(spec.path, packageName + '-' + version)
+        var packagePath
+        // If version is an array, first arg is NPM path and second is alias.
+        if (version.constructor === Array) {
+          packagePath = path.join(spec.path, packageName + '-' + version[1])
+        } else {
+          packagePath = path.join(spec.path, packageName + '-' + version)
+        }
         return RSVP.resolve()
           .then(function() {
             if (!fs.existsSync(packagePath)) {
               console.log(packageName + ' ' + version + ': Installing')
               fs.mkdirSync(packagePath)
               fs.mkdirSync(path.join(packagePath, 'node_modules'))
-              var cp = spawn('npm', ['install', packageName + '@' + version], {
+
+              var installName;
+              // If version is an array, first arg is NPM path and second is alias.
+              if (version.constructor === Array) {
+                installName = version[0]
+              } else {
+                installName = packageName + '@' + version
+              }
+
+              var cp = spawn('npm', ['install', installName], {
                 cwd: packagePath,
                 stdio: 'inherit',
                 timeout: 300