Block patterns: Any way to reset the pattern to whatever is in the code?

It would heavily depend on your block layout and how you format your block data & inner blocks.

When using the deprecation, you just need to think of it like making an acceptable format to recognise your old markup, with a migrate function if you need to help the conversion along.

Add all your old attributes and if you need to do anything more complicated (like parsing and converting inner blocks, or adding attributes etc… then use the migrate function.

const { registerBlockType } = wp.blocks;

registerBlockType('gutenberg/block-with-deprecated-version', {
    // ... other block properties go here

    attributes: {
        content: {
            type: 'string',
            default: 'some random value',
        },
    },

    save(props) {
        return <ul>{{{ -- new block save stuff -- }}}</ul>;
    },

    deprecated: [
        { // Essentially a copy of your old attributes and save function goes here
            attributes: { // These will be the 'old' attributes - 
                content: {
                    type: 'string',
                    default: 'some random value',
                },
            },

            save( props ) {
                return <div>{{{-- OLD block save stuff -- }}}</div>; 
            },
        },
    ],
});

There are some examples shown on the Codex