I haven't tried doing a new checkout, but in my SVN working directory that I was happily managing with Xcode 6.4, after upgrading to Xcode 7 and then to El Capitan, I can no longer view the modified files in the project history window. Each time I select the "Show N modified file(s)" button, the differencing window opens but then, after selecting a particular file, I get a "The source control operation failed because no working copy could be found" error alert panel. Git operations also seem broken on some of my Git working copies (not all of them, but most of them). The problem is also in Xcode 7.1 beta 3. I don't know whether it was the El Capitan upgrade that screwed things up, but I have two machines that exhibit the same behavior.
I've filed a bug report but I haven't seen any review activity on it yet. It's very exasperating why each "upgrade" seems to keep breaking fundamental things that weren't broken beforehand.
Same here. It appears that SVN support on Xcode 7.0 and 7.1 is broken. Right now I have to use xcode 6.4 for doing branch merges as well as checking file history. This is going to be a big problem for me soon, because I'm getting a new mac with El Capitan and Xcode 6.4 won't run on it*.
*Edit: Xcode 6.4 can still be used for source control on El Capitan.
Bug # 23742220 filed for broken modified history viewing bug.