version/update system: version.sh, --update flag, UPDATE_MODULES, auto-detect existing install

lib/tui-fs.sh

@@ -182,3 +182,30 @@ tui_fs_confirm_start() {
   [[ "$response" =~ ^[yY](es)?$ ]]
   return $?
 }
+
+tui_fs_ask_update() {
+  local date="$1"
+  [[ "$TUI_FS_ACTIVE" -eq 0 ]] && return 1
+
+  tput cup 4 0 2>/dev/null || true
+  tput ed 2>/dev/null || true
+
+  printf '  \033[1;36m┌─\033[0m  \033[1;37mExisting Installation Found\033[0m\n'
+  printf '  \033[1;36m│\033[0m\n'
+  printf '  \033[1;36m│\033[0m  Installed: \033[1;37m%s\033[0m\n' "$date"
+  printf '  \033[1;36m│\033[0m  Update applies new dotfiles, packages and config\n'
+  printf '  \033[1;36m│\033[0m  without re-running GPU/fresh-install setup.\n'
+  printf '  \033[1;36m└─\033[0m\n'
+  printf '\n'
+  printf '  \033[1;36m?\033[0m  Update existing installation? \033[1m[Y/n]\033[0m '
+
+  if ((OMERON_HAS_GUM)); then
+    gum confirm "Update existing installation?"
+    return $?
+  fi
+
+  read -r response
+  response="${response:-Y}"
+  [[ "$response" =~ ^[yY](es)?$ ]]
+  return $?
+}