If you get that kind of error:
ArgumentError (parent directory is world writable, FileUtils#remove_entry_secure does not work; abort: "/tmp/gitosis20121120-26282-1q9qa73" (parent directory mode 40777)):
Check for permissions for /tmp directory. remove_entry_secure accepts world-writable directory in a path only if it’s /tmp, but only if that directory has 1777 permissions.