Automatically update a download's version number and change log using a readme.txt file with the Easy Digital Downloads Software Licensing extension.

readme.php

<?php
/*
Plugin Name: EDD Readme Parsing Enhancements
Description: Updates a Download's current version and change log fields when using the readme.txt parsing feature in Easy Digital Downloads.
*/

/**
 * Filters the EDD readme.txt parser response and updates the
 * download's current version and change log fields.
 */
function array_edd_readme_enchancer( $response, $download, $readme ) {

	// Update the current version number for the theme
	$meta_version = get_post_meta( $download->ID, '_edd_sl_version', true );
	if ( '' != $readme['stable_tag'] && $meta_version != $readme['stable_tag'] ) {
		update_post_meta( $download->ID, '_edd_sl_version', $readme['stable_tag'] );
	}

	// Update the change log field so we can display it on the front end.
	$meta_changelog = get_post_meta( $download->ID, '_edd_sl_changelog', true );
	if( '' != $readme['sections']['change_log'] && $meta_changelog != $readme['sections']['change_log'] ) {
		update_post_meta( $download->ID, '_edd_sl_changelog', $readme['sections']['change_log'] );
	}

	return $response;

}
add_filter( 'edd_sl_license_readme_response', 'array_edd_readme_enchancer', 10, 3 );