Do laws have changelogs
@polychrome not quite the same but this github project for the US Constitution is pretty cool https://github.com/JesseKPhillips/USA-Constitution/commit/be6888349900ec3301198bf6e468c44f5acf9fff
@polychrome I can only speak to the area of the law I'm most familiar with, which is about retirement plans, but the answer is typically yes. For example here is IRC sec. 401: https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title26-section401&num=0&edition=prelim. If you go to paragraph (a)(9) titled "Required Distributions" you will see references to age 72. Before 2020, it used to be age 70½. Scroll further down to the Amendments section of the page and under 2019 you will see that Pub. L. 116–94 (aka the 2020 appropriations bill) changed those sections.
@polychrome Legislation is patches.
Ful legal code can reference that, and there are several technical projects to do so as others have noted.