In actual git you'd do this with a .gitattributes file, defining a specific executable to do the diff. The docs show it being done with a docx (by converting to text) and a png (using its metadata): https://git-scm.com/book/en/v2/Customizing-Git-Git-Attribute...
I've used musdex in "actual git" with the aforementioned hooks. It works pretty well. There are some advantage to the chosen hooks approach rather than a git attributes-based approach especially that it is more "portable": GitHub doesn't need to have musdex installed to view "musdexed" repositories and you get the nicer merge/diff behaviors from standard diff/merge in PRs and commit views and everywhere. Also, while it is much less of a performance boost compared to darcs, git still benefits in some cases of pack file delta compression/optimization due to smaller differences in "musdexed" text/XML files rather than binary containers.
I have one public example of this on my GitHub that comes to mind, but it's a particularly weird one because it uses a musdex plugin to extract/combine an already non-binary format. (In this case it was an Inform 7 story.ni file that I just preferred to source control as lots of smaller, column-wrapped "chapter" files rather than one long "book" file of run-on paragraphs. GitHub's cool modern code browser hasn't been taught how to do jump to section for Inform 7 story.ni files, so it is nice being able to browse it as a file tree instead. Similar it's nice to see commit diffs broken down by chapter. I can't install my own Inform 7 plugin to GitHub's website, but I can certainly reshape my repo with a tool like musdex.)
