Command for fetching file contents

[simonw]

Something like this:

github-to-sqlite files github.db simonw/datasette

This would fetch all files from the main branch into a files table.

Additional options could handle things like pulling files from a branch or tag, or just pulling files that match a specific glob or that exist in a specific directory.

[simonw]

Given rate limits (see #51) this command might be better implemented by running a git clone into a temporary directory - doing so would retrieve all of the files in one go.