t0006 & t5000: prepare for 64-bit timestamps

Git's source code refers to timestamps as unsigned longs. On 32-bit
platforms, as well as on Windows, unsigned long is not large enough to
capture dates that are "absurdly far in the future".

It is perfectly valid by the C standard, of course, for the `long` data
type to refer to 32-bit integers. That is why the `time_t` data type
exists: so that it can be 64-bit even if `long` is 32-bit. Git's source
code simply uses an incorrect data type for timestamps, is all.

The earlier quick fix 6b9c38e14cd (t0006: skip "far in the future" test
when unsigned long is not long enough, 2016-07-11) papered over this
issue simply by skipping the respective test cases on platforms where
they would fail due to the data type in use.

This quick fix, however, tests for *long* to be 64-bit or not. What we
need, though, is a test that says whether *whatever data type we use for
timestamps* is 64-bit or not.

The same quick fix was used to handle the similar problem where Git's
source code uses `unsigned long` to represent size, instead of `size_t`,
conflating the two issues.

So let's just add another prerequisite to test specifically whether
timestamps are represented by a 64-bit data type or not. Later, after we
switch to a larger data type, we can flip that prerequisite to test
`time_t` instead of `long`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/t/helper/test-date.c b/t/helper/test-date.c
index 506054bcd..4727bea25 100644
--- a/t/helper/test-date.c
+++ b/t/helper/test-date.c
@@ -4,7 +4,8 @@ static const char *usage_msg = "\n"
 "  test-date relative [time_t]...\n"
 "  test-date show:<format> [time_t]...\n"
 "  test-date parse [date]...\n"
-"  test-date approxidate [date]...\n";
+"  test-date approxidate [date]...\n"
+"  test-date is64bit\n";
 
 static void show_relative_dates(const char **argv, struct timeval *now)
 {
@@ -93,6 +94,8 @@ int cmd_main(int argc, const char **argv)
 		parse_dates(argv+1, &now);
 	else if (!strcmp(*argv, "approxidate"))
 		parse_approxidate(argv+1, &now);
+	else if (!strcmp(*argv, "is64bit"))
+		return sizeof(unsigned long) == 8 ? 0 : 1;
 	else
 		usage(usage_msg);
 	return 0;