mirror/ git
1
0
Fork 0
mirror of https://github.com/git/git.git synced 2024-05-19 01:16:08 +02:00
Code

date: use localtime() for "-local" time formats 

When we convert seconds-since-epochs timestamps into a
broken-down "struct tm", we do so by adjusting the timestamp
according to the known offset and then using gmtime() to
break down the result. This means that the resulting struct
"knows" that it's in GMT, even though the time it represents
is adjusted for a different zone. The fields where it stores
this data are not portably accessible, so we have no way to
override them to tell them the real zone info.

For the most part, this works. Our date-formatting routines
don't pay attention to these inaccessible fields, and use
the same tz info we provided for adjustment. The one
exception is when we call strftime(), whose %Z format
reveals this hidden timezone data.

We solved that by always showing the empty string for %Z.
This is allowed by POSIX, but not very helpful to the user.
We can't make this work in the general case, as there's no
portable function for setting an arbitrary timezone (and
anyway, we don't have the zone name for the author zones,
only their offsets).

But for the special case of the "-local" formats, we can
just skip the adjustment and use localtime() instead of
gmtime(). This makes --date=format-local:%Z work correctly,
showing the local timezone instead of an empty string.

The new test checks the result for "UTC", our default
test-lib value for $TZ. Using something like EST5 might be
more interesting, but the actual zone string is
system-dependent (for instance, on my system it expands to
just EST). Hopefully "UTC" is vanilla enough that every
system treats it the same.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2017-06-15 09:52:17 -04:00 committed by Junio C Hamano
parent 22280d7ee7
commit 6eced3ec5e
2 changed files with 13 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
date.c
View File

@ -60,6 +60,12 @@ static struct tm *time_to_tm(unsigned long time, int tz)
return gmtime(&t);
}
static struct tm *time_to_tm_local(unsigned long time)
{
time_t t = time;
return localtime(&t);
}
/*
* What value of "tz" was in effect back then at "time" in the
* local timezone?
@ -201,7 +207,10 @@ const char *show_date(unsigned long time, int tz, const struct date_mode *mode)
return timebuf.buf;
}
tm = time_to_tm(time, tz);
if (mode->local)
tm = time_to_tm_local(time);
else
tm = time_to_tm(time, tz);
if (!tm) {
tm = time_to_tm(0, 0);
tz = 0;
@ -233,7 +242,8 @@ const char *show_date(unsigned long time, int tz, const struct date_mode *mode)
month_names[tm->tm_mon], tm->tm_year + 1900,
tm->tm_hour, tm->tm_min, tm->tm_sec, tz);
else if (mode->type == DATE_STRFTIME)
strbuf_addftime(&timebuf, mode->strftime_fmt, tm, tz, "");
strbuf_addftime(&timebuf, mode->strftime_fmt, tm, tz,
mode->local ? NULL : "");
else
strbuf_addf(&timebuf, "%.3s %.3s %d %02d:%02d:%02d %d%c%+05d",
weekday_names[tm->tm_wday],

1
t/t0006-date.sh
View File

@ -56,6 +56,7 @@ check_show unix-local "$TIME" '1466000000'
check_show 'format:%z' "$TIME" '+0200'
check_show 'format-local:%z' "$TIME" '+0000'
check_show 'format:%Z' "$TIME" ''
check_show 'format-local:%Z' "$TIME" 'UTC'
check_show 'format:%%z' "$TIME" '%z'
check_show 'format-local:%%z' "$TIME" '%z'