single input file with directory

[displague]

Rather than recursively loading all files in a directory, an option should exist to merge a directory and a starting file. The existing behavior should also be retained.

For example:

public.yml
private.yml
public/components/schemas/foo.yml
public/components/paths/foo.yml
private/components/schemas.foo.yml
private/components/paths/foo.yml

With this layout, developers could potentially $ref: ../../public definitions in their private spec.
They may then wish to only generate the private or public spec:

oas_contrib merge --base=public.yml ./ outfile.yml