Merge branch 'dt/untracked-subdir' into maint

The experimental untracked-cache feature were buggy when paths with a few levels of subdirectories are involved. * dt/untracked-subdir: untracked cache: fix entry invalidation untracked-cache: fix subdirectory handling t7063: use --force-untracked-cache to speed up a bit untracked-cache: support sparse checkout