fix(async): register the git prompt async handler correctly (#12267)

This fix conditionally registers the git prompt async handler only
if `git_prompt_info` is used anywhere in the prompt variables.

This is done in the proper order, so that the async request is
processed once the handler has been registered.

This fix also passes the return value of the previous command
to each of the async handlers, in case they are needed.

lib/git.zsh

@@ -40,11 +40,29 @@ function _omz_git_prompt_status() {
 # Enable async prompt by default unless the setting is at false / no
 if zstyle -t ':omz:alpha:lib:git' async-prompt; then
   function git_prompt_info() {
-    _omz_register_handler _omz_git_prompt_status
     if [[ -n "$_OMZ_ASYNC_OUTPUT[_omz_git_prompt_status]" ]]; then
       echo -n "$_OMZ_ASYNC_OUTPUT[_omz_git_prompt_status]"
     fi
   }
+
+  # Conditionally register the async handler, only if it's needed in $PROMPT
+  # or any of the other prompt variables
+  function _defer_async_git_register() {
+    # Check if git_prompt_info is used in a prompt variable
+    case "${PS1}:${PS2}:${PS3}:${PS4}:${RPS1}:${RPS2}:${RPS3}:${RPS4}" in
+    *(\$\(git_prompt_info\)|\`git_prompt_info\`)*)
+      _omz_register_handler _omz_git_prompt_status
+      return
+      ;;
+    esac
+
+    add-zsh-hook -d precmd _defer_async_git_register
+    unset -f _defer_async_git_register
+  }
+
+  # Register the async handler first. This needs to be done before
+  # the async request prompt is run
+  precmd_functions=(_defer_async_git_register $precmd_functions)
 else
   function git_prompt_info() {
     _omz_git_prompt_status