diff-local against the working copy leaves out new documents #1709

What happens: for MPR v2, mxcli diff-local -p app.mpr --ref <before> reports "0 new, 3 modified" while dozens of new, untracked unit files exist under mprcontents/.
Repro: add a module with new pages and flows without committing, then run diff-local --ref HEAD.
Expected: untracked units are listed as new.
Version: 0.28.0.

Mendix 11.12.4.