osutil: more cleanups
- eliminate a level of nesting
- untab targets of gotos
# should print nothing# should failabort: path 'b/x' is inside repo 'b'abort: path 'b/x' is inside repo 'b'# should failabort: path 'b/x' is inside repo 'b'# should arguably print nothing# should failabort: path 'b/a' is inside repo 'b'