Undivert update-initramfs more carefully

Previously the wrapper script and diversion were left in place on images
such as buildd images that don't have initramfs-tools installed.

LP: #1841573

debian/changelog

@@ -1,3 +1,11 @@
+livecd-rootfs (2.606) UNRELEASED; urgency=medium
+
+  * Undivert update-initramfs more carefully: previously the wrapper script
+    and diversion were left in place on images such as buildd images that
+    don't have initramfs-tools installed (LP: #1841573).
+
+ -- Colin Watson <cjwatson@ubuntu.com>  Tue, 27 Aug 2019 12:43:55 +0100
+
 livecd-rootfs (2.605) eoan; urgency=medium
 
   [ David Krauser ]

live-build/auto/build

@@ -284,6 +284,7 @@ EOF
 		divert_grub chroot
 		divert_update_initramfs
 		lb chroot "$@"
+		undivert_update_initramfs
 		undivert_grub chroot
 	fi
 

live-build/functions

@@ -875,13 +875,12 @@ echo "update-initramfs: diverted by livecd-rootfs (will be called later)" >&2
 exit 0
 EOF
 	chmod +x chroot/usr/sbin/update-initramfs
+}
 
-	cat > config/hooks/999-undivert-update-initramfs.chroot <<'EOF'
+undivert_update_initramfs () {
-#! /bin/sh
+	rm -f chroot/usr/sbin/update-initramfs
-[ ! -f /usr/sbin/update-initramfs.REAL ] && exit 0
+	Chroot chroot "dpkg-divert --quiet --remove --rename \
-rm -f /usr/sbin/update-initramfs
+		/usr/sbin/update-initramfs"
-dpkg-divert --quiet --remove --rename /usr/sbin/update-initramfs
-EOF
 }
 
 is_root_layer () {

live-build/lb_chroot_layered

@@ -261,6 +261,11 @@ create_chroot_pass () {
 	lb chroot_dpkg remove ${*}
 	lb chroot_debianchroot remove ${*}
 
+	# Restore update-initramfs, if necessary
+	if $(is_root_layer $pass); then
+		undivert_update_initramfs
+	fi
+
 	# Restore grub
 	undivert_grub chroot