t7812: test PCRE2 whitespace bug
Check if git grep works around the PCRE2 big fixed by their
e0c6029
(Fix inifinite loop when a single byte newline is searched in JIT.,
2020-05-29), which affects version 10.35 and earlier.
Searching for leading whitespace also triggers the endless loop.
Set a one-second alarm to abort in case we do get hit by the bug, to
avoid having to wait forever for the test result.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>