Should escaping the share root be allowed?

Most functions in `dir.go` use the `path` function to get the path to the directory entry that is to be worked on.
```go
fi, err := os.Stat(d.path(p))
```

`d` is used as the base directory, with `p` joined to it using `path` -- the question is, should escaping this base directory be allowed?

The same goes for
```go
os.Rename(p, filepath.Join(base, filepath.FromSlash(name)))
```