Plain old update files maybe. You name each zip release with a number and a date. For example #1 will be dated today. Each time you update you increase the #

Plain old update files maybe. You name each zip release with a number and a date. For example #1 will be dated today. Each time you update you increase the # by 1 and mark the date. You provide seperate small update files named #2 update, #3 update. If I had downloaded the full archive #1, I can just download #2 and #3 update and have the latest version. If I never downloaded the library I can just download the most recent version and then keep it updated using update files.