I was perusing the shared extractor the other day, when I came across
the `NodeInfo` struct. I noticed that the `fields` and `subtypes` fields
on this struct had two seemingly identical ways of expressing the same
thing: `None` and `Some(empty)` (where `empty` is respectively the empty
map and the empty vector). As far as I can tell, there's no semantic
difference in either case, so we can just elide the option type entirely
and use the empty value directly. This has the nice side-effect of
cleaning up some of the other code.
Replace the `file_extensions` field with `file_globs`, which supports
UNIX style glob patterns powered by the `globset` crate.
This allows files with no extension (e.g. Dockerfiles) to be extracted,
by specifying a glob such as `*Dockerfile`.
One surprising aspect of this change is that the globs match against the
whole path, rather than just the file name.
This is a breaking change.
