support/scripts: reject skeletons or overlays that are unexpectedly merged

Currently, we partially accept that a skeleton or a rootfs overlay be
merged:
  - for unmerged, we accept all kind of situations: unmerged, partially
    merged, badly merged, merged-usr or merged-bin, arbitrary relative
    or absolute symlinks, and whatnots;
  - for merged-usr, we strictly require a properly set up merged-usr,
    and we refuse a merged-bin;
  - for merged-bin, we stricty require a properly set up merged-bin.

The unmerged case is inconsistent with the other cases, especially it
allows for arbitrary symlinks that may point to arbitrary locations that
may even not belong to $(TARGET_DIR) at all...

We fix that by ensuring that the skeleton and overlays strictly adhere
to the merge-level of the configuration; i.e. for an unmerged config, we
require that the skeleton and overlays be strictly unmerged, that is,
/bin, /lib, and /sbin, and their counterparts in /usr, are actual
directories.

Thus, for all three types of merge level, the skeleton and overlays must
match the configured merge level.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Romain Naour <romain.naour@smile.fr>

support/scripts/check-merged

@@ -3,16 +3,21 @@
 # Check if a given custom skeleton or overlay complies to the merged
 # requirements:
 #
-# - for merged-usr:
-#   /bin            missing, or a relative symlink to usr/bin
-#   /lib            missing, or a relative symlink to usr/lib
-#   /sbin           missing, or a relative symlink to usr/sbin
+# - for unmerged:
+#   /bin            missing*, or an existing directory; not a symlink
+#   /lib            missing*, or an existing directory; not a symlink
+#   /sbin           missing*, or an existing directory; not a symlink
 #   /usr/bin/       missing*, or an existing directory; not a symlink
 #   /usr/lib/       missing*, or an existing directory; not a symlink
 #   /usr/sbin/      missing*, or an existing directory; not a symlink
 #
 # *: must be present for skeletons, can be missing for overlays
 #
+# - for merged-usr: all of the above, except:
+#   /bin            missing, or a relative symlink to usr/bin
+#   /lib            missing, or a relative symlink to usr/lib
+#   /sbin           missing, or a relative symlink to usr/sbin
+#
 # - for merged-bin: all of the above, except:
 #   /usr/sbin       missing, or a relative symlink to bin (thus points
 #                   to /usr/bin)
@@ -119,9 +124,9 @@ test_dir() {
 is_success=true
 for root; do
 	first=true
+	test_dir "${type}" "${root}" "/" "usr/bin"
+	test_dir "${type}" "${root}" "/" "usr/lib"
 	if ${merged_usr}; then
-		test_dir "${type}" "${root}" "/" "usr/bin"
-		test_dir "${type}" "${root}" "/" "usr/lib"
 		test_merged "${type}" "${root}" "/" "bin" "usr/bin"
 		test_merged "${type}" "${root}" "/" "lib" "usr/lib"
 		test_merged "${type}" "${root}" "/" "sbin" "usr/sbin"
@@ -130,6 +135,11 @@ for root; do
 		else
 			test_dir "${type}" "${root}" "/" "usr/sbin"
 		fi
+	else
+		test_dir "${type}" "${root}" "/" "bin"
+		test_dir "${type}" "${root}" "/" "lib"
+		test_dir "${type}" "${root}" "/" "sbin"
+		test_dir "${type}" "${root}" "/" "usr/sbin"
 	fi
 done