Stop `linkup` from backing up the same symlink

If a symlink already points where we want it, do not copy it to backup.
This makes the install scripts' output less cluttered.

bin/linkup

@@ -10,5 +10,6 @@ tgt=${2:?$usage}
 bak=~/.backup
 
 [[ ! -d $bak ]] && mkdir $bak
+[[ -L "$tgt" && "$(readlink $tgt)" = "$src" ]] && exit
 [[ -e "$tgt" ]] && mv -v "$tgt" "$bak/${tgt##*/}-$(date '+%Y%m%d-%H%M%S')" || true
 ln -sfv "$src" "$tgt"

bin/zfs-backup

@@ -31,7 +31,7 @@ echo "Next Snapshot: $nextSnap"
 echo ""
 
 # Same snapshot? Nothing to do.
-[[ $prevSnap == $nextSnap ]] && echo "Not backing up." && exit
+[[ $prevSnap = $nextSnap ]] && echo "Not backing up." && exit
 
 # pv check: displays transfer speed during backup.
 hasPv=$(command -v pv || true)
@@ -75,7 +75,7 @@ echo "ZFS Sending/Receiving done."
 if [[ -n $prevSnap ]]; then
   echo $'\nDestroy previous snapshot and finalise backup? (y/n)'
   read ANS
-  if [[ $ANS == "y" ]]; then
+  if [[ $ANS = "y" ]]; then
     zfs destroy -R $fsFrom@$prevSnap
     zfs destroy -R $fsTo@$prevSnap
   fi