Read lastrv in one step, now that the file will exist

dotfiles/bash/post.bashrc

@@ -10,8 +10,7 @@
 
 __make_ps1d() {
     local rvfile="/var/tmp/bash-rv/$$.lastrv"
-    local lastrv
-    read lastrv <<<$(cat $rvfile 2>/dev/null)
+    local lastrv=$(cat $rvfile)
     local do_rm=false
     test "$1" == "-r" && do_rm=true
     if [ 0$lastrv -gt 0 ];