[PATCH v6 2/8] t0006 & t5000: prepare for 64-bit timestamps

[Johannes Schindelin]

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.schinde...@gmx.de>
---
 t/helper/test-date.c | 5 ++++-
 t/t0006-date.sh      | 4 ++--
 t/t5000-tar-tree.sh  | 6 +++---
 t/test-lib.sh        | 2 ++
 4 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/t/helper/test-date.c b/t/helper/test-date.c
index 506054bcd5d..4727bea255c 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;
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index c0c910867d7..9539b425ffb 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -53,8 +53,8 @@ check_show unix-local "$TIME" '1466000000'
 
 # arbitrary time absurdly far in the future
 FUTURE="5758122296 -0400"
-check_show iso       "$FUTURE" "2152-06-19 18:24:56 -0400" LONG_IS_64BIT
-check_show iso-local "$FUTURE" "2152-06-19 22:24:56 +0000" LONG_IS_64BIT
+check_show iso       "$FUTURE" "2152-06-19 18:24:56 -0400" TIME_IS_64BIT
+check_show iso-local "$FUTURE" "2152-06-19 22:24:56 +0000" TIME_IS_64BIT
 
 check_parse() {
        echo "$1 -> $2" >expect
diff --git a/t/t5000-tar-tree.sh b/t/t5000-tar-tree.sh
index 886b6953e40..997aa9dea28 100755
--- a/t/t5000-tar-tree.sh
+++ b/t/t5000-tar-tree.sh
@@ -390,7 +390,7 @@ test_expect_success TAR_HUGE,LONG_IS_64BIT 'system tar can 
read our huge size' '
        test_cmp expect actual
 '
 
-test_expect_success LONG_IS_64BIT 'set up repository with far-future commit' '
+test_expect_success TIME_IS_64BIT 'set up repository with far-future commit' '
        rm -f .git/index &&
        echo content >file &&
        git add file &&
@@ -398,11 +398,11 @@ test_expect_success LONG_IS_64BIT 'set up repository with 
far-future commit' '
                git commit -m "tempori parendum"
 '
 
-test_expect_success LONG_IS_64BIT 'generate tar with future mtime' '
+test_expect_success TIME_IS_64BIT 'generate tar with future mtime' '
        git archive HEAD >future.tar
 '
 
-test_expect_success TAR_HUGE,LONG_IS_64BIT 'system tar can read our future 
mtime' '
+test_expect_success TAR_HUGE,TIME_IS_64BIT 'system tar can read our future 
mtime' '
        echo 4147 >expect &&
        tar_info future.tar | cut -d" " -f2 >actual &&
        test_cmp expect actual
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 13b5696822d..beee1d847ff 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1164,3 +1164,5 @@ build_option () {
 test_lazy_prereq LONG_IS_64BIT '
        test 8 -le "$(build_option sizeof-long)"
 '
+
+test_lazy_prereq TIME_IS_64BIT 'test-date is64bit'
-- 
2.12.2.windows.2.406.gd14a8f8640f