title: How to find duplicate keys in localizable.strings files automatically?
body: <p>When using localizable.strings with many entries in your XCode project you sooner or later may use a key more than once. Is it possible to let XCode find that case and issue a warning about it?</p>
  
  <p>Apple's <a href="https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/LoadingResources/Strings/Strings.html" rel="noreferrer">Resource Programming</a> mentions the genstrings tool, but usually you don't use that yourself in XCode. So, how can I let XCode detect duplicate keys in such files without manually running genstrings?</p>
  
  <p><strong>Bounty note:</strong> to earn the bounty a solution must fully integrate with XCode if it uses external resources like scripts, that is, it must work with input files given in XCode, mark a build as fail in case of duplicates and must not trigger for false positives like empty lines or comments.</p>