Workaround if apt-config shell returns an empty string

Author: pillarsdotnet

templates/update_had_no_effect.sh.epp

@@ -4,13 +4,13 @@
   Integer $tries = 1,
 | -%>
 
-DIR='var/cache/apt'
 EVAL="$(mktemp)" || EVAL=/tmp/aptdir
 apt-config shell DIR Dir::Cache > "$EVAL" && . "$EVAL"
+[ "$DIR" ] || DIR='var/cache/apt'
 cd "/$DIR" || exit 0
 export TMPDIR="/$DIR"
-CUR=pkgcache.bin
 apt-config shell CUR DIR::Cache::pkgcache >"$EVAL" && . "$EVAL"
+[ "$CUR" ] || CUR=pkgcache.bin
 OLD="$(mktemp)" || OLD="/${DIR}/${CUR}.old"
 rm -f "$EVAL"
 ln -f "$CUR" "$OLD"