Merge branch 'js/ask-yesno'

* js/ask-yesno: git-gui--askyesno (mingw): use Git for Windows' icon, if available git-gui--askyesno: allow overriding the window title git gui: set GIT_ASKPASS=git-gui--askpass if not set yet git-gui: provide question helper for retry fallback on Windows Signed-off-by: Johannes Sixt <j6t@kdbg.org>