how to create a snapshot using Xcode 7?
I opened a bug regarding this. According to Apple, "Snapshots have been removed in Xcode 7. You can export existing snapshots in Xcode 7 but not create or restore them."
Hopefully they'll restore them in a future release, but for now I recommend using git from the Source Control menu as suggested by Tim.
there isn't snapshot in xcode 7, to resolve this problem, use xcode 6 and 7, xcode 6 to create and restore snapshot and after you can open your project with xcode 7.
For posterity - in the menu at the top select "SourceControl" then "Commit...", add a comment and "Commit X Files" then after you make additional changes and want to see the changes select "SourceControl" and "Commit" and select the file on the left.
All explained nicely in :http://www.raywenderlich.com/51351/how-to-use-git-source-control-with-xcode-in-ios-7