Further 'approxidate' improvements

The previous patch to improve approxidate got us to the point that a lot
of the remaining annoyances were due to the 'strict' date handling running
first, and deciding that it got a good enough date that the approximate
date routines were never even invoked.

For example, using a date string like

	6AM, June 7, 2009

the strict date logic would be perfectly happy with the "June 7, 2009"
part, and ignore the 6AM part that it didn't understand - resulting in the
information getting dropped on the floor:

	6AM, June 7, 2009 -> Sat Jun 6 00:00:00 2009

and the date being calculated as if it was midnight, and the '6AM' having
confused the date routines into thinking about '6 June' rather than 'June
7' at 6AM (ie notice how the _day_ was wrong due to this, not just the
time).

So this makes the strict date routines a bit stricter, and requires that
not just the date, but also the time, has actually been parsed. With that
fix, and trivial extension of the approxidate routines, git now properly
parses the date as

	6AM, June 7, 2009 -> Sun Jun  7 06:00:00 2009

without dropping the fuzzy time ("6AM" or "noon" or any of the other
non-strict time formats) on the floor.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

date.c

@@ -24,6 +24,8 @@ time_t tm_to_time_t(const struct tm *tm)
 		return -1;
 	if (month < 2 || (year + 2) % 4)
 		day--;
+	if (tm->tm_hour < 0 || tm->tm_min < 0 || tm->tm_sec < 0)
+		return -1;
 	return (year * 365 + (year + 1) / 4 + mdays[month] + day) * 24*60*60UL +
 		tm->tm_hour * 60*60 + tm->tm_min * 60 + tm->tm_sec;
 }
@@ -425,13 +427,19 @@ static int match_multi_number(unsigned long num, char c, const char *date, char
 	return end - date;
 }
 
-/* Have we filled in any part of the time/date yet? */
+/*
+ * Have we filled in any part of the time/date yet?
+ * We just do a binary 'and' to see if the sign bit
+ * is set in all the values.
+ */
 static inline int nodate(struct tm *tm)
 {
-	return tm->tm_year < 0 &&
-		tm->tm_mon < 0 &&
-		tm->tm_mday < 0 &&
-		!(tm->tm_hour | tm->tm_min | tm->tm_sec);
+	return (tm->tm_year &
+		tm->tm_mon &
+		tm->tm_mday &
+		tm->tm_hour &
+		tm->tm_min &
+		tm->tm_sec) < 0;
 }
 
 /*
@@ -580,6 +588,9 @@ int parse_date(const char *date, char *result, int maxlen)
 	tm.tm_mon = -1;
 	tm.tm_mday = -1;
 	tm.tm_isdst = -1;
+	tm.tm_hour = -1;
+	tm.tm_min = -1;
+	tm.tm_sec = -1;
 	offset = -1;
 	tm_gmt = 0;
 
@@ -893,6 +904,17 @@ static void pending_number(struct tm *tm, int *num)
 		*num = 0;
 		if (tm->tm_mday < 0 && number < 32)
 			tm->tm_mday = number;
+		else if (tm->tm_mon < 0 && number < 13)
+			tm->tm_mon = number-1;
+		else if (tm->tm_year < 0) {
+			if (number > 1969 && number < 2100)
+				tm->tm_year = number - 1900;
+			else if (number > 69 && number < 100)
+				tm->tm_year = number;
+			else if (number < 38)
+				tm->tm_year = 100 + number;
+			/* We screw up for number = 00 ? */
+		}
 	}
 }