The pattern this API uses in C is to allow the input parameters
pointer targets to be `NULL`, and it doesn't return values in that
case.
A further complexity here is that the API will still return `NULL`
for symbolic links.
But Rust can't express this pattern as is, so we were always
returning values but in `Option<T>` wrappers that the caller needed
to unwrap for the metadata.
(We really want an even more efficient API here that avoids the glib
objects entirely, e.g. no reason not to pass directly back a type
that lets Rust directly read from the fd for bare repos, but
that can come later)
I want to write APIs that *require* the caller to have set up
an ostree transaction. It's natural to require passing a guard
to do so. But then we want an accessor for the repo.
Luca BRUNO
Colin Walters