Avoid diff cost on "git log -z"

diff --git a/date.c b/date.c
index 542c004c2e8d2a9f731a1f303cc3393d88f5a6e8..4690371e5559f72b7755b3cc92ae85843098d285 100644 (file)
--- a/date.c
+++ b/date.c
@@ -55,12 +55,38 @@ static struct tm *time_to_tm(unsigned long time, int tz)
        return gmtime(&t);
 }
 
-const char *show_date(unsigned long time, int tz, int relative)
+/*
+ * What value of "tz" was in effect back then at "time" in the
+ * local timezone?
+ */
+static int local_tzoffset(unsigned long time)
+{
+       time_t t, t_local;
+       struct tm tm;
+       int offset, eastwest;
+
+       t = time;
+       localtime_r(&t, &tm);
+       t_local = my_mktime(&tm);
+
+       if (t_local < t) {
+               eastwest = -1;
+               offset = t - t_local;
+       } else {
+               eastwest = 1;
+               offset = t_local - t;
+       }
+       offset /= 60; /* in minutes */
+       offset = (offset % 60) + ((offset / 60) * 100);
+       return offset * eastwest;
+}
+
+const char *show_date(unsigned long time, int tz, enum date_mode mode)
 {
        struct tm *tm;
        static char timebuf[200];
 
-       if (relative) {
+       if (mode == DATE_RELATIVE) {
                unsigned long diff;
                struct timeval now;
                gettimeofday(&now, NULL);
@@ -102,15 +128,24 @@ const char *show_date(unsigned long time, int tz, int relative)
                /* Else fall back on absolute format.. */
        }
 
+       if (mode == DATE_LOCAL)
+               tz = local_tzoffset(time);
+
        tm = time_to_tm(time, tz);
        if (!tm)
                return NULL;
-       sprintf(timebuf, "%.3s %.3s %d %02d:%02d:%02d %d %+05d",
-               weekday_names[tm->tm_wday],
-               month_names[tm->tm_mon],
-               tm->tm_mday,
-               tm->tm_hour, tm->tm_min, tm->tm_sec,
-               tm->tm_year + 1900, tz);
+       if (mode == DATE_SHORT)
+               sprintf(timebuf, "%04d-%02d-%02d", tm->tm_year + 1900,
+                               tm->tm_mon + 1, tm->tm_mday);
+       else
+               sprintf(timebuf, "%.3s %.3s %d %02d:%02d:%02d %d%c%+05d",
+                               weekday_names[tm->tm_wday],
+                               month_names[tm->tm_mon],
+                               tm->tm_mday,
+                               tm->tm_hour, tm->tm_min, tm->tm_sec,
+                               tm->tm_year + 1900,
+                               (mode == DATE_LOCAL) ? 0 : ' ',
+                               tz);
        return timebuf;
 }
 
@@ -379,9 +414,11 @@ static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
        num = strtoul(date, &end, 10);
 
        /*
-        * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
+        * Seconds since 1970? We trigger on that for any numbers with
+        * more than 8 digits. This is because we don't want to rule out
+        * numbers like 20070606 as a YYYYMMDD date.
         */
-       if (num > 946684800) {
+       if (num >= 100000000) {
                time_t time = num;
                if (gmtime_r(&time, tm)) {
                        *tm_gmt = 1;