checks if babel is installed globally and displays correct cli message (#5258)

* checks if babel is installed globally and displays correct cli message - fixes #5228

* recommend local installation and fix lint errors

* uses babel-cli vs babel

* switch back to babel

* use process.cwd() to determine if globally executed

* checks for /node_module/.bin/babel

* compare execPath and module execution path to determine global or local installation

* Move the babel/cli.js into a 'src' so the 'const's are compiled Node < 6.

packages/babel/package.json

@@ -7,8 +7,8 @@
   "license": "MIT",
   "repository": "https://github.com/babel/babel/tree/master/packages/babel",
   "bin": {
-    "babel": "./cli.js",
-    "babel-node": "./cli.js",
-    "babel-external-helpers": "./cli.js"
+    "babel": "./lib/cli.js",
+    "babel-node": "./lib/cli.js",
+    "babel-external-helpers": "./lib/cli.js"
   }
 }

packages/babel/src/cli.js

@@ -1,10 +1,13 @@
 #!/usr/bin/env node
+import path from "path";
+
+const globalMessage = path.dirname(process.execPath) === path.dirname(process.env._ || "") ? " -g" : "";
 
 console.error("You have mistakenly installed the `babel` package, which is a no-op in Babel 6.\n" +
   "Babel's CLI commands have been moved from the `babel` package to the `babel-cli` package.\n" +
   "\n" +
-  "    npm uninstall babel\n" +
-  "    npm install babel-cli\n" +
+  "    npm uninstall" + globalMessage + " babel\n" +
+  "    npm install --save-dev babel-cli\n" +
   "\n" +
   "See http://babeljs.io/docs/usage/cli/ for setup instructions.");
 process.exit(1);