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If you try to clean your missing files warnings from Xcode following the
The missing file warning on Xcode 4 guide
soon you will hit
svn command not found (on mountain lion).
You get this because the svn has moved in Xcode developer package.
In order to solve this and get back to your usual way of working you have to add the new path to your
/etc/path
Jump to the marvellous guide of Three Eyed Bird and follow this detailed guide.