Add tmux_attach_start script zsh completions

Will autocomplete with currently open tmux sessions.

tmux/.config/zsh/completions/_tmux_attach_start

@@ -0,0 +1,12 @@
+#compdef _tmux_attach_start
+#
+# Requires tmux_attach_start script in path
+#
+# Enables completion for zsh of tmux_attach_start function
+# with currently open sessions, or tmux options.
+
+_tmux_attach_start() {
+  _alternative \
+    "sessions:user sessions:($(tmux list-sessions -F'#{session_name}' 2>/dev/null))"
+}
+

tmux/.local/bin/tmux_attach_start

@@ -120,6 +120,7 @@ _attach_or_create() {
   if ! _session_exists; then
     _create_detached_session
     # look for .tmux.session file if no file has been explicitly passed in
+    # session files always take precedence over environment files when specifically passed in
     if ! _file_exists "$session_file"; then
       _load_env_session_file
     fi