[PATCH v3] Allow commit date before Unix epoch, clean fix for (issue2513)

[Adrian Buehlmann]

On 2016-04-02 20:28, Florent Gallaire wrote:
> # HG changeset patch
> # User Florent Gallaire <fgallaire at gmail.com>
> # Date 1459621582 -7200
> #      Sat Apr 02 20:26:22 2016 +0200
> # Node ID a415db6cb545dc312019cd919dbbe7e2b7cbe0f9
> # Parent  ff0d3b6b287f89594bd8d0308fe2810d2a18ea01
> date: reallow negative timestamp, fix for Windows buggy gmtime() (issue2513)
> 
> DVCS are very useful to store various texts (as legislation) written before
> Unix epoch. Fri, 13 Dec 1901 is a nice gain over Thu, 01 Jan 1970.
> Revert dd24f3e7ca9e and e1002cf9fe54.
> 
> diff -r ff0d3b6b287f -r a415db6cb545 mercurial/util.py
> --- a/mercurial/util.py    Tue Mar 29 12:29:00 2016 -0500
> +++ b/mercurial/util.py    Sat Apr 02 20:26:22 2016 +0200
> @@ -1578,9 +1578,6 @@
>      number of seconds away from UTC. if timezone is false, do not
>      append time zone to string."""
>      t, tz = date or makedate()
> -    if t < 0:
> -        t = 0   # time.gmtime(lt) fails on Windows for lt < -43200
> -        tz = 0
>      if "%1" in format or "%2" in format or "%z" in format:
>          sign = (tz > 0) and "-" or "+"
>          minutes = abs(tz) // 60
> @@ -1589,11 +1586,15 @@
>          format = format.replace("%1", "%c%02d" % (sign, q))
>          format = format.replace("%2", "%02d" % r)
>      try:
> -        t = time.gmtime(float(t) - tz)
> -    except ValueError:
> +        # Never use time.gmtime() and datetime.datetime.fromtimestamp()
> +        # because they use the gmtime() system call which is buggy on Windows
> +        # for negative values.
> +        t = datetime.datetime(1970, 1, 1) + datetime.timedelta(seconds=t - tz)
> +    except OverflowError:

Note: If I understand docs.python.org correctly, OverflowError can only
happen if the result of the sum would have a year smaller than 1
(datetime.MINYEAR) or larger than 9999 (datetime.MAXYEAR).

>          # time was out of range
> -        t = time.gmtime(sys.maxint)
> -    s = time.strftime(format, t)
> +        t = (datetime.datetime(1970, 1, 1) +
> +             datetime.timedelta(seconds=cmp(t, 0) * 0x7fffffff))
> +    s = t.strftime(format)

Nitpick: Since you don't use time.gmtime any more, clamping to the magic
year-2038-value on OverflowError is... a little bit strange.

Perhaps, it would make more sense to clamp to the limits of
datetime.datetime instead? Or explicitly check that t is within the
bounds of

datetime.datetime(1970, 1, 1) + datetime.timedelta(0x7fffffff)
datetime.datetime(1970, 1, 1) + datetime.timedelta(-0x7fffffff)

?

(see also c208dcd0f709, which introduced the original clamping for the
time.gmtime call)

>      return s
> 
>  def shortdate(date=None):
> @@ -1714,8 +1715,6 @@
>      # to UTC+14
>      if abs(when) > 0x7fffffff:
>          raise Abort(_('date exceeds 32 bits: %d') % when)
> -    if when < 0:
> -        raise Abort(_('negative date value: %d') % when)
>      if offset < -50400 or offset > 43200:
>          raise Abort(_('impossible time zone offset: %d') % offset)
>      return when, offset
> diff -r ff0d3b6b287f -r a415db6cb545 tests/test-commit.t
> --- a/tests/test-commit.t    Tue Mar 29 12:29:00 2016 -0500
> +++ b/tests/test-commit.t    Sat Apr 02 20:26:22 2016 +0200
> @@ -27,8 +27,8 @@
>    $ hg commit -d '111111111111 0' -m commit-7
>    abort: date exceeds 32 bits: 111111111111
>    [255]
> -  $ hg commit -d '-7654321 3600' -m commit-7
> -  abort: negative date value: -7654321
> +  $ hg commit -d '-111111111111 0' -m commit-7
> +  abort: date exceeds 32 bits: -111111111111
>    [255]
> 
>  commit added file that has been deleted