[PATCH v5 0/8] Introduce timestamp_t for timestamps

[Johannes Schindelin <johannes.schindelin@gmx.de>]

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 makes the date_overflows() check more stringent again.

It is arguably a bug to paper over too-large author/committer dates and
to replace them with Jan 1 1970 without even telling the user that we do
that, but this is the behavior that t4212 verifies, so I reinstated that
behavior. The change in behavior was missed because of the missing
unsigned_add_overflows() test.

Changes since v4:

- in gm_time_t(), we now test specifically that the timezone adjustment
  neither underflows nor overflows.

- the patch introduced in v4 that tried to defer the date_overflows()
  check to gm_time_t() rather than replacing the ident timestamp by a 0
  without any warning was dropped again: it broke t4212.


Johannes Schindelin (8):
  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

 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                                        | 113 ++++++++++++++------------
 fetch-pack.c                                  |   8 +-
 fsck.c                                        |   2 +-
 git-compat-util.h                             |   9 ++
 http-backend.c                                |   4 +-
 parse-options-cb.c                            |   4 +-
 pretty.c                                      |   4 +-
 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, 260 insertions(+), 219 deletions(-)


base-commit: e2cb6ab84c94f147f1259260961513b40c36108a
Published-As: https://github.com/dscho/git/releases/tag/time_t-may-be-int64-v5
Fetch-It-Via: git fetch https://github.com/dscho/git time_t-may-be-int64-v5

Interdiff vs v4:

 diff --git a/date.c b/date.c
 index 75f6335cd09..63fa99685e2 100644
 --- a/date.c
 +++ b/date.c
 @@ -47,9 +47,16 @@ static time_t gm_time_t(timestamp_t time, int tz)
  	minutes = (minutes / 100)*60 + (minutes % 100);
  	minutes = tz < 0 ? -minutes : minutes;
  
 -	if (date_overflows(time + minutes * 60))
 +	if (minutes > 0) {
 +		if (unsigned_add_overflows(time, minutes * 60))
 +			die("Timestamp+tz too large: %"PRItime" +%04d",
 +			    time, tz);
 +	} else if (time < -minutes * 60)
 +		die("Timestamp before Unix epoch: %"PRItime" %04d", time, tz);
 +	time += minutes * 60;
 +	if (date_overflows(time))
  		die("Timestamp too large for this system: %"PRItime, time);
 -	return (time_t)time + minutes * 60;
 +	return (time_t)time;
  }
  
  /*
 diff --git a/pretty.c b/pretty.c
 index 35fd290096a..587d48371b0 100644
 --- a/pretty.c
 +++ b/pretty.c
 @@ -410,10 +410,14 @@ 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 (ident->tz_begin && ident->tz_end)
 -		tz = strtol(ident->tz_begin, NULL, 10);
 -	if (tz >= INT_MAX || tz <= INT_MIN)
 -		tz = 0;
 +	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;
 +	}
  	return show_date(date, tz, mode);
  }
  

-- 
2.12.2.windows.2.406.gd14a8f8640f