title: Is the project.xcworkspace file important?
body: <p>I am doing command line xcodebuild using a shell script.  My problem is if I open and close the <code>xx.xcodeproj</code> file once and then use that command it works well.</p>
  
  <p>Somehow if I get deep into the file changes, this <code>project.xcworkspace</code> is the only file that has changed.  Is this file valid and should I check it into version control?
  Will this cause any issues?</p>
  
  <p>I've heard that it's as important as <code>.pbxproj</code>: is this true?</p>
  
  <p>I couldn't find any valid documentation which talks about the roles and responsibilities of various files in the xcode project files.  Please provide links which help me to understand that.</p>