A little Ruby script to package another script as an OS X Application.

package.rb

require 'fileutils'

if Dir.exists? "App.app"
  puts "Nope"
  exit
end

FileUtils.mkpath "App.app/Contents/MacOS"
FileUtils.mkpath "App.app/Contents/Resources"

info_plist = %Q[
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>CFBundleExecutable</key>
  <string>run.sh</string>
  <key>CFBundleIconFile</key>
  <string>app.icns</string>
  <key>CFBundleInfoDictionaryVersion</key>
  <string>1.0</string>
  <key>CFBundlePackageType</key>
  <string>APPL</string>
  <key>CFBundleSignature</key>
  <string>????</string>
  <key>CFBundleVersion</key>
  <string>1.0</string>
</dict>
</plist>
]

File.open("App.app/Contents/Info.plist", 'w') { |f| f.write(info_plist) }

run_sh = %Q[#!/bin/bash

say hi

# Add RVM to $PATH
[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm"

# Add rbenv to $PATH
export PATH="$HOME/.rbenv/bin:$PATH"

# Change working path
cd "$(dirname "$0")/../Resources/"

# Start app
ruby app.rb
]

File.open("App.app/Contents/MacOS/run.sh", 'w') { |f| f.write(run_sh) }

File.chmod(0777, "App.app/Contents/MacOS/run.sh")

# Copy all files to Resources
FileUtils.cp_r(Dir["app/*"], "App.app/Contents/Resources")