Bad DWIM response when git gui cannot start

If git cannot start one of the external commands (at least some of them), the DWIM engine is a bit flaky:

   $ git citool
   /usr/local/libexec/git-core/git-citool: line 10: exec: wish: not found
   git: 'citool' is not a git-command. See 'git --help'.

   Did you mean this?
       citool

   $ git gui
   /usr/local/libexec/git-core/git-gui: line 10: exec: wish: not found
   git: 'gui' is not a git-command. See 'git --help'.

   Did you mean this?
       gui