[PATCH v4 0/9] Introduce timestamp_t for timestamps

Git v2.9.2 was released in a hurry to accomodate for platforms like Windows, where the `unsigned long` data type is 32-bit even for 64-bit setups.

The quick fix was to simply disable all the testing with "absurd" future dates.

However, we can do much better than that, as we already make use of 64-bit data types internally. There is no good reason why we should not use the same for timestamps. Hence, let's use uintmax_t for timestamps.

Note: while the `time_t` data type exists and is meant to be used for
timestamps, on 32-bit Linux it is *still* 32-bit. An earlier iteration
used `time_t` for that reason, but it came with a few serious downsides:
as `time_t` can be signed (and indeed, on Windows it is an int64_t),
Git's expectation that 0 is the minimal value does no longer hold true,
introducing its own set of interesting challenges. Besides, if we *can*
handle far in the future timestamps (except for formatting them using
the system libraries), it is more consistent to do so.

The upside of using `uintmax_t` for timestamps is that we do a much better job to support far in the future timestamps across all platforms, including 32-bit ones. The downside is that those platforms that use a 32-bit `time_t` will barf when parsing or formatting those timestamps.

This iteration has two fixes for issues reported by Travis CI (thank deity for Continuous Testing, eh?), one by the MacOSX nodes (but not by the Linux nor the Windows nodes), the other by the windows node (which reminds me to run tests after rebasing to `master` not only in a Linux VM but also on Windows, even if it takes ages there due to the heavy shell scripting).

After reading Junio's comments on the cover letter of v2, I had another look at the usage of date_overflows() and was able to relax two of them.

Changes since v3:

- fixed the fix in archive-zip.c that tried to report a too large
  timestamp (and would have reported the uninitialized time_t instead)

- adjusted the so-far forgotten each_reflog() function (that was
  introduced after v1, in 80f2a6097c4 (t/helper: add test-ref-store to
  test ref-store functions, 2017-03-26)) to use timestamp_t and PRItime,
  too

- removed the date_overflows() check from time_to_tm(), as it calls
  gm_time_t() which already performs that check

- the date_overflows() check in show_ident_date() was removed, as we do
  not know at that point yet whether we use the system functions to
  render the date or not (and there would not be a problem in the latter
  case)

Johannes Schindelin (9):
  ref-filter: avoid using `unsigned long` for catch-all data type
  t0006 & t5000: prepare for 64-bit timestamps
  t0006 & t5000: skip "far in the future" test when time_t is too
    limited
  Specify explicitly where we parse timestamps
  Introduce a new "printf format" for timestamps
  Introduce a new data type for timestamps
  Abort if the system time cannot handle one of our timestamps
  Use uintmax_t for timestamps
  show_date_ident(): defer date overflow check

 Documentation/technical/api-parse-options.txt |   8 +-
 archive-tar.c                                 |   5 +-
 archive-zip.c                                 |  12 ++-
 archive.h                                     |   2 +-
 builtin/am.c                                  |   4 +-
 builtin/blame.c                               |  14 ++--
 builtin/fsck.c                                |   6 +-
 builtin/gc.c                                  |   2 +-
 builtin/log.c                                 |   4 +-
 builtin/merge-base.c                          |   2 +-
 builtin/name-rev.c                            |   6 +-
 builtin/pack-objects.c                        |   4 +-
 builtin/prune.c                               |   4 +-
 builtin/receive-pack.c                        |  14 ++--
 builtin/reflog.c                              |  24 +++---
 builtin/rev-list.c                            |   2 +-
 builtin/rev-parse.c                           |   2 +-
 builtin/show-branch.c                         |   4 +-
 builtin/worktree.c                            |   4 +-
 bundle.c                                      |   4 +-
 cache.h                                       |  14 ++--
 commit.c                                      |  18 ++---
 commit.h                                      |   2 +-
 config.c                                      |   2 +-
 credential-cache--daemon.c                    |  12 +--
 date.c                                        | 106 ++++++++++++++------------
 fetch-pack.c                                  |   8 +-
 fsck.c                                        |   2 +-
 git-compat-util.h                             |   9 +++
 http-backend.c                                |   4 +-
 parse-options-cb.c                            |   4 +-
 pretty.c                                      |  16 ++--
 reachable.c                                   |   9 +--
 reachable.h                                   |   4 +-
 ref-filter.c                                  |  22 +++---
 reflog-walk.c                                 |   8 +-
 refs.c                                        |  14 ++--
 refs.h                                        |   8 +-
 refs/files-backend.c                          |   8 +-
 revision.c                                    |   6 +-
 revision.h                                    |   4 +-
 sha1_name.c                                   |   6 +-
 t/helper/test-date.c                          |  18 +++--
 t/helper/test-parse-options.c                 |   4 +-
 t/helper/test-ref-store.c                     |   4 +-
 t/t0006-date.sh                               |   4 +-
 t/t5000-tar-tree.sh                           |   6 +-
 t/test-lib.sh                                 |   3 +
 tag.c                                         |   6 +-
 tag.h                                         |   2 +-
 upload-pack.c                                 |   8 +-
 vcs-svn/fast_export.c                         |   8 +-
 vcs-svn/fast_export.h                         |   4 +-
 vcs-svn/svndump.c                             |   2 +-
 wt-status.c                                   |   2 +-
 55 files changed, 257 insertions(+), 227 deletions(-)

base-commit: 6a2c2f8d34fa1e8f3bb85d159d354810ed63692e
Published-As: https://github.com/dscho/git/releases/tag/time_t-may-be-int64-v4
Fetch-It-Via: git fetch https://github.com/dscho/git time_t-may-be-int64-v4

Interdiff vs v3:

 diff --git a/archive-zip.c b/archive-zip.c
 index bb117a74d45..68df3d64402 100644
 --- a/archive-zip.c
 +++ b/archive-zip.c
 @@ -551,7 +551,8 @@ static void dos_time(timestamp_t *timestamp, int *dos_date, int *dos_time)
  	struct tm *t;
  
  	if (date_overflows(*timestamp))
 -		die("Timestamp too large for this system: %"PRItime, time);
 +		die("timestamp too large for this system: %"PRItime,
 +		    *timestamp);
  	time = (time_t)*timestamp;
  	t = localtime(&time);
  	*timestamp = time;
 diff --git a/date.c b/date.c
 index db3435df3e4..75f6335cd09 100644
 --- a/date.c
 +++ b/date.c
 @@ -43,12 +43,12 @@ static time_t gm_time_t(timestamp_t time, int tz)
  {
  	int minutes;
  
 -	if (date_overflows(time))
 -		die("Timestamp too large for this system: %"PRItime, time);
 -
  	minutes = tz < 0 ? -tz : tz;
  	minutes = (minutes / 100)*60 + (minutes % 100);
  	minutes = tz < 0 ? -minutes : minutes;
 +
 +	if (date_overflows(time + minutes * 60))
 +		die("Timestamp too large for this system: %"PRItime, time);
  	return (time_t)time + minutes * 60;
  }
  
 @@ -59,12 +59,7 @@ static time_t gm_time_t(timestamp_t time, int tz)
   */
  static struct tm *time_to_tm(timestamp_t time, int tz)
  {
 -	time_t t;
 -
 -	if (date_overflows(time))
 -		die("Timestamp too large for this system: %"PRItime, time);
 -
 -	t = gm_time_t((time_t)time, tz);
 +	time_t t = gm_time_t(time, tz);
  	return gmtime(&t);
  }
  
 diff --git a/pretty.c b/pretty.c
 index 587d48371b0..35fd290096a 100644
 --- a/pretty.c
 +++ b/pretty.c
 @@ -410,14 +410,10 @@ const char *show_ident_date(const struct ident_split *ident,
  
  	if (ident->date_begin && ident->date_end)
  		date = parse_timestamp(ident->date_begin, NULL, 10);
 -	if (date_overflows(date))
 -		date = 0;
 -	else {
 -		if (ident->tz_begin && ident->tz_end)
 -			tz = strtol(ident->tz_begin, NULL, 10);
 -		if (tz >= INT_MAX || tz <= INT_MIN)
 -			tz = 0;
 -	}
 +	if (ident->tz_begin && ident->tz_end)
 +		tz = strtol(ident->tz_begin, NULL, 10);
 +	if (tz >= INT_MAX || tz <= INT_MIN)
 +		tz = 0;
  	return show_date(date, tz, mode);
  }
  
 diff --git a/t/helper/test-ref-store.c b/t/helper/test-ref-store.c
 index 2d84c45ffe9..9077ec2c330 100644
 --- a/t/helper/test-ref-store.c
 +++ b/t/helper/test-ref-store.c
 @@ -138,10 +138,10 @@ static int cmd_for_each_reflog(struct ref_store *refs, const char **argv)
  }
  
  static int each_reflog(struct object_id *old_oid, struct object_id *new_oid,
 -		       const char *committer, unsigned long timestamp,
 +		       const char *committer, timestamp_t timestamp,
  		       int tz, const char *msg, void *cb_data)
  {
 -	printf("%s %s %s %lu %d %s\n",
 +	printf("%s %s %s %"PRItime" %d %s\n",
  	       oid_to_hex(old_oid), oid_to_hex(new_oid),
  	       committer, timestamp, tz, msg);
  	return 0;