Replace suite name with alias in sources.list

This keeps the image at the same major release even in case of later
stable releases.

bootstrap.sh

@@ -34,7 +34,7 @@ install -m 0755 -o root -g root scripts/* $rootfs/$bindir
 
 for script in $(ls $rootfs/$bindir); do
     echo "+ /$bindir/$script"
-    chroot $rootfs /$bindir/$script
+    chroot $rootfs /$bindir/$script $suite
 done
 
 chroot $rootfs apt-get --purge autoremove -q -y

scripts/tweak-apt-sources

@@ -0,0 +1,22 @@
+#!/bin/sh -eu
+# tweak-apt-sources -- to use alias instead of suite name
+# Copyright (C) 2017  Olaf Meeuwissen
+#
+# License: GPL-3.0+
+
+DIR=/
+ETC=etc/apt
+SOURCES=sources.list
+
+eval $(apt-config shell DIR Dir)
+eval $(apt-config shell ETC Dir::Etc)
+eval $(apt-config shell SOURCES Dir::Etc::sourcelist)
+
+cfg=$DIR$ETC$SOURCES
+
+suite=$1
+alias=$(cat /etc/devuan_version)
+
+sed -i "s/$suite/$alias/" $cfg
+
+rm $0