That's what I get for not fully testing lmao! But right, paths in shell scripts are relative to the working directory, and if I want to be relative to the script I gotta use dirname!
Sat down and thought about the structure here and how to make the full/delta stuff make more sense together! Here's what I came up with!
In both full and delta archiving, we prepare the manifest, we create the local archive, then we upload it to remote.