git-gui had some cygwin cleanups this cycle: https://github.com/prati0100/git-gui/compare/a5005ded43149a67290c9b8e83d585daf23716ef...b85c5a4ec66f18fdaa550fdf7801f48ebbc4292f This broke our hacky workarounds. This tries to add "cygwin-git-under-windows-tk" case for all the relevant places. If there is something no longer working that worked before, please let me know.