art-cli public API.

CLI command parsing and dispatch.

Non-lazily drives the rendering of batches.

File and path handling common to this ART CLI library in general.

Logging facility used by this library. Consumers of this library may bind
the logging fn vars to their extant logging functions.

Uniform ART messages throughout CLI tooling.

Resolvers of CLI option arguments.

If an argument doesn't appear to be resolvable according to the nature of
a given resolver fn, it returns nil. Otherwise, these fns proceed with
resolution and will signal any errors encountered as :vivid.art.cli/error
conditions, :normally nil for production but managed by the condition
system for use in automated testing.

As an example, a file resolver function interprets its argument as a file
path. If the file doesn't exist, the resolver fn sensibly returns nil, but
if the file does exist, then any errors associated with attempting to read
the file's contents is signalled.

Validation of individual options available in public API & CLI