Swift 3 / Xcode 8 Upgrade - 100's of DerivedData files missing from working copy errors

Question

I have just upgraded to the latest Beta version of XCode and Swift but after using the converter my app project now has over 200 build time yellow errors all stating /\"projectD

Answer 1

I had a rogue .git folder in a parent folder that didn't 'go' to anything-

verify under "Source Control" menu that all of your "Working Copies" actually connect to a real source control folder

NONE of these 'solutions' worked for me, except this removing rogue .git folder