Difftastic is a structural diffing tool that understands syntax:

Difftastic is a CLI diff tool that compares files based on their syntax, not line-by-line. Difftastic produces accurate diffs that are easier for humans to read.

Unfortunately, Difftastic did not understand HEEx templates syntax well, so changes were not highlighted properly. I’ve submitted a pull request to fix this which is now merged, so any Elixir dev using Difftastic should see improved diffing for HEEx templates.

https://crbelaus.com/2025/02/10/better-elixir-diffs-with-difftastic