Merge branch 'jc/epochtime-wo-tz' into maint-2.3

"git commit --date=now" or anything that relies on approxidate lost
the daylight-saving-time offset.

* jc/epochtime-wo-tz:
  parse_date_basic(): let the system handle DST conversion
  parse_date_basic(): return early when given a bogus timestamp

Author: gitster

date.c

@@ -704,20 +704,24 @@ int parse_date_basic(const char *date, unsigned long *timestamp, int *offset)
 		date += match;
 	}
 
-	/* mktime uses local timezone */
+	/* do not use mktime(), which uses local timezone, here */
 	*timestamp = tm_to_time_t(&tm);
+	if (*timestamp == -1)
+		return -1;
+
 	if (*offset == -1) {
-		time_t temp_time = mktime(&tm);
+		time_t temp_time;
+
+		/* gmtime_r() in match_digit() may have clobbered it */
+		tm.tm_isdst = -1;
+		temp_time = mktime(&tm);
 		if ((time_t)*timestamp > temp_time) {
 			*offset = ((time_t)*timestamp - temp_time) / 60;
 		} else {
 			*offset = -(int)((temp_time - (time_t)*timestamp) / 60);
 		}
 	}
 
-	if (*timestamp == -1)
-		return -1;
-
 	if (!tm_gmt)
 		*timestamp -= *offset * 60;
 	return 0; /* success */