> At this point, the question is: why keep files as blobs in the first place. If a revision control system stores AST trees instead, all the work is AST-level.

The problem is that disks (and storage in general) store only bytes so you inherently need to deal with bytes at some point. You could view source code files as the serialization of the AST (or other parse tree).

This is especially apparent with LISPs and their sexprs, but equally applies to other languages too.