Re-organise to use a bare repo

Re-organise to use a bare repo, e.g.
https://www.atlassian.com/git/tutorials/dotfiles.

.zsh/configs/tmux.zsh

@@ -0,0 +1,22 @@
+_not_inside_tmux() {
+  [[ -z "$TMUX" ]]
+}
+
+_not_inside_phpstorm() {
+  if is_macos; then
+    # VS Code returns "vscode".
+    # iTerm returns "iTerm.app".
+    # PhpStorm returns nothing.
+    [[ "$TERM_PROGRAM" != "" ]]
+  elif is_linux; then
+    [[ "$TERMINAL_EMULATOR" != "JetBrains"* ]]
+  fi
+}
+
+ensure_tmux_is_running() {
+  if _not_inside_tmux && _not_inside_phpstorm; then
+    tat
+  fi
+}
+
+ensure_tmux_is_running