MinGW's bash does not recognize an exit code -1 as failure. See also 47e3de0e (MinGW: truncate exit()'s argument to lowest 8 bits) and 2488df84
(builtin run_command: do not exit with -1). Exit code 1 is good enough.
Signed-off-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>