If you run Xcode 7 on Yosemite (regardless of which Beta) and attempt a Git Source Control action, it causes a crash of an Xcode task in the background. However, run the same thing on El Capitan and it works fine.
Running Xcode 7 on Yosemite and Source Control
See this thread: https://forums.developer.apple.com/message/24783#24783 - had to remove all repositories under Preferences > Accounts from Xcode 6 then launch Xcode 7.