Add snaps to manifest

Make sure that all the snaps are listed in the full manifest of each
layer and as delta in the delta manifest.

live-build/auto/build

@@ -481,8 +481,10 @@ EOF
 
 	# Create layered squashfs system
 	CURPASS=1
+	PREVPASS=""
 	LASTPASS=$(echo $PASSES|wc -w)
 	prev_manifest=""
+	to_remove=""
 	if [ "${IMAGEFORMAT:-}" = live-layered ]; then
 		for _PASS in $PASSES
 		do
@@ -493,11 +495,25 @@ EOF
       			mksquashfs . ${squashfs_f} \
         		-no-progress -xattrs -comp xz )
 
+			# Full manifest until that PASS
+			# Note: snaps won't be listed in the new layer by snap-seed-parse
+			# if no newly snap was installed in that layer. Copy and then remove it
+			# just to create the correct full manifest and avoid a new layer
+			# chroot mount dance.
+			SNAPPATH=var/lib/snapd/seed/seed.yaml
+			if [ ! -f "chroot.${_PASS}/${SNAPPATH}" ] && [ -n "${PREVPASS}" ] && [ -f "chroot.${PREVPASS}/${SNAPPATH}" ]; then
+				mkdir -p chroot.${_PASS}/$(dirname ${SNAPPATH})
+				cp "chroot.${PREVPASS}/${SNAPPATH}" "chroot.${_PASS}/${SNAPPATH}"
+				to_remove="chroot.${_PASS}/var/lib/snapd ${to_remove}"
+			fi
 			squashfs_f_manifest="${base}.manifest"
 			create_manifest "chroot.${_PASS}/" "${squashfs_f_manifest}.full"
-			# We want manifest to only contain the diff of current pass
+
+			# Delta manifest
 			diff -NU0 ${prev_manifest}.full ${squashfs_f_manifest}.full|grep -v ^@ > $squashfs_f_manifest
 			prev_manifest=$squashfs_f_manifest
+
+			# Full ISO manifest
 			if [ $CURPASS -eq $LASTPASS ]; then
 				cp "${squashfs_f_manifest}.full" livecd.${PROJECT}.manifest
 			fi
@@ -505,8 +521,12 @@ EOF
 			squashfs_f_size="${base}.size"
 			du -B 1 -s "chroot.${_PASS}/" | cut -f1 > "${squashfs_f_size}"
 
+			PREVPASS=${_PASS}
 			CURPASS=$(( CURPASS + 1 ))
 		done
+		if [ -n "${to_remove}" ]; then
+			rm -r ${to_remove}
+		fi
 	fi
 
 	# Teardown mount points in layered mode