Hi! I’ve pushed it with a copyright line for you, and with a unit test for ‘union-build’ with #:create-all-directories? #t:
https://git.savannah.gnu.org/cgit/guix.git/commit/?id=addce19e2d38a197f5ea10eefb5f3cd25c3a52e7 https://git.savannah.gnu.org/cgit/guix.git/commit/?id=0a5ce0d1df3befa2c4e018e84da3bd66c9eac48d Thank you! Ludo’.