Updates the node formula example to properly use the installed node v…

…ersion

The existing example uses a symlink which means that whatever `node` is first in the PATH will be used. This can mean that a Homebrew-installed nodejs executable may not work reliably (since it may execute with a different version of node)

This PR changes it so that using the Homebrew-installed `node` will be used. It also includes common other options (like shell completion) as well as the old symlink solution.

docs/Node-for-Formula-Authors.md

@@ -102,7 +102,17 @@ class Foo < Formula
 
   def install
     system "npm", "install", *Language::Node.std_npm_install_args(libexec)
-    bin.install_symlink Dir["#{libexec}/bin/*"]
+
+    # "link" the executable `foo`, ensuring that the version of node installed by Homebrew is used
+    # (the created `foo` will set the ENV before exec'ing your executable)
+    env = { PATH: "#{HOMEBREW_PREFIX/"bin"}:$PATH"  }
+    (bin/"foo").write_env_script "#{libexec}/bin/foo", env
+
+    # Uncomment if you simply want to symlink the executable – note that this means the first `node` on the PATH will be used
+    # bin.install_symlink Dir["#{libexec}/bin/*"]
+
+    # Uncomment if you want to write the completion scripts for bash, fish, and zsh (assuming your executable has a command "completion" which returns a completion script)
+    # generate_completions_from_executable(libexec/"bin/foo", "completion", base_name: 'foo')
   end
 
   test do