test-context: Exercise some corner cases for merging filesystems
test-context: Exercise some corner cases for merging filesystems

Signed-off-by: Simon McVittie <0e1aea601907c1a85c2dc96e5ea37e23c58d2e9b@collabora.com>
Co-authored-by: Alexander Larsson <8c32c4b573bb86be9076a894bc9e0dfe2b512e8a@redhat.com>
(cherry picked from commit fab0f8ed7c52fc58e6c550d123ede9621c760ca7)

flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak