shrc: tx: use switch-client if already in tmux session

shrc

@@ -665,15 +665,18 @@ __realpath(){
 
 tx(){
     tmux start-server
-    if test $# -eq 0
+    if test -z "$1"
     then
-        echo ":: tx <session> to attach."
-        tmux ls
-    elif tmux has -t "$1"
+        echo "usage: tx <session_name>"
+        tmux list-sessions
+    elif test -z "$TMUX"
     then
-        tmux attach -t "$1"
+        # -A: attach if already exists
+        tmux new-session -A -c "$HOME" -s "$1"
     else
-        tmux new -s "$1"
+        # create new session if not exists yet
+        tmux has-session -t "$1" || TMUX= tmux new-session -d -c "$HOME" -s "$1"
+        tmux switch-client -t "$1"
     fi
 }