ui: kill most users of parentui name and arg, replace with .copy()
# 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'