BasePathFile.Name trimmed only filepath.Clean(path) from the wrapped
file name. filepath.Clean drops the trailing separator, and a nested
BasePathFile reports a name whose base segment is preceded by a leading
separator (for example "/123/x"), which the cleaned base ("123") does
not match. The base then leaked into Name and callers double-prepended
it. Trim the separator-prefixed form too so nested BasePathFs report a
name that round-trips.
Fixes#428
dualfroz
upstream