Stop littering; use `local` where possible

dotfiles/bash/post.bashrc

 ### '''' ###
 
 __make_ps1d() {
-    rvfile="/var/tmp/bash-rv/$$.lastrv"
-    lastrv=$(cat $rvfile)
+    local rvfile="/var/tmp/bash-rv/$$.lastrv"
+    local lastrv=$(cat $rvfile)
     if [ $lastrv -gt 0 ];
     then
         echo "$lastrv"
 make_ps1() {
     # these functions must be already defined by ~/.bash/user/*.bashrc
     # and ~/.bash/host/*.bashrc
-    svrc='$(__save_rv $?)'
-    ps1u=$(make_ps1u)
-    ps1h=$(make_ps1h)
-    ps1w="$lblue\w$normal";
-    ps1G='$(__git_ps1 "(%s)")';
-    ps1g="$green$ps1G$normal";
-    ps1D='$(__make_ps1d)';
-    ps1d="$lred$ps1D$normal";
+    local svrc='$(__save_rv $?)'
+    local ps1u=$(make_ps1u)
+    local ps1h=$(make_ps1h)
+    local ps1w="$lblue\w$normal";
+    local ps1G='$(__git_ps1 "(%s)")';
+    local ps1g="$green$ps1G$normal";
+    local ps1D='$(__make_ps1d)';
+    local ps1d="$lred$ps1D$normal";
     echo "$svrc$ps1u@$ps1h:$ps1w$ps1g$ps1d\$ ";
 }