Xcode is showing multiple working copies:
Working Copies
myProject - master
myProject_olderRepo
myProject_originalRepo
The second two are g
If you have Git repositories showing up, then you must have a *.xcscmblueprint file somewhere in your project. For me, it was in my workspace and not in a project. From terminal window:
% find . -name '*.xcscmblueprint'
./TaskMe.xcworkspace/xcshareddata/TaskMe.xcscmblueprint
Edit that file with care to keep just the entry you want. Or perhaps better, just delete the file and add back the repository you want.