https://reddiepoint.github.io/RedAlt-SteamUp-Documentation/
RedAlt SteamUp Creator provides users with a convenient alternative for creating and installing Steam updates without the need for xDelta patches. It downloads the files changed between builds, listed in the SteamDB changelist, with Depot Downloader. Updates created using RedAlt SteamUp Creator allow for updating from any build between the specified initial build, to the final build. For example, if the update was created for Build 10000000 to Build 10000010, then the update would be compatible with builds 10000000-10000009 (although some files would be redundant).
For instructions on how to use RedAlt SteamUp Creator, see the instructions.