install.sh: improve

install.sh

@@ -12,13 +12,13 @@ git submodule update --init --recursive
 
 # if these aren't links, move them out of the way?
 for f in ~/.zshrc ~/.profile; do
-  if [ -f $f ]; then
+  if [ -f "$f" ]; then
-    mv $f $f.orig
+    mv "$f" "$f.orig"
   fi
 done
 
-if [ -n $1 ]; then
+if [ -n "$1" ]; then
-  $STOW -t $HOME $1
+  $STOW -t $HOME "$1"
   exit 1
 fi
 
@@ -36,6 +36,6 @@ for dir in  \
   tmux \
   zsh
 do
-  $STOW -t ~/ $dir
+  $STOW -t $HOME $dir
 done