I think ALL explicit options should over-ride options that were detected in the directory structure. This means my current implementation isn't quite right - using a class method makes it hard to merge the details with the explicit options passed to the CLI function.

I'm going to add a Datasette(config_dir=".") parameter which initializes from the given directory, allowing other parameters to over-ride it.

I think documentation goes on https://datasette.readthedocs.io/en/stable/config.html - but I'm going to need to re-arrange that page to fit in a section about configuration directories.

I'll move the existing list of settings into a "configration options" section.