tests: add some tests for directory whiteouts

I wrote this trying to reproduce a bug, and couldn't. But hey, maybe it'll
catch a bug someday...

Signed-off-by: Tycho Andersen <tycho@tycho.pizza>

Author: tych0

test/dir-whiteout.bats

@@ -0,0 +1,42 @@
+load helpers
+
+function setup() {
+    stacker_setup
+}
+
+function teardown() {
+    cleanup
+}
+
+@test "dir whiteouts work" {
+    cat > stacker.yaml <<EOF
+base:
+    from:
+        type: oci
+        url: $UBUNTU_OCI
+    run: |
+        mkdir /hello-base
+mid:
+    build_only: true
+    from:
+        type: built
+        tag: base
+    run: |
+        mkdir /foo
+        touch /foo/bar
+top:
+    from:
+        type: built
+        tag: mid
+    run: |
+        rm -f /foo/bar
+        rmdir /foo
+EOF
+    stacker build
+
+    umoci unpack --image oci:top top
+    ls top/rootfs
+    false
+    [ ! -f top/rootfs/foo/bar ]
+    [ ! -d top/rootfs/foo ]
+}