After merging, I checked with git status and cleaned with git clean -rf, but I was still left with the following untracked file:
<projectName>.xcodeproj/xcuserdata/<username>.xcuserdatad/xcdebugger/
I then checked to see if it would be cleaned with git clean -n, and there was nothing shown, as expected (since it was not cleaned in the previous command).
Also, I have tried an alternative, that I touch .gitignore and added xcuserdata in the .gitignore file. Afterwards when I checked for git status, the untracked file becomes .gitignore, effectively substituting the previous untracked file, which still did not really solve my problem.
What should be the way so that I can clean up my working tree?