approxidate_careful() reports errorneous date string

For a long time, the time based reflog syntax (e.g. master@{yesterday})
didn't complain when the "human readable" timestamp was misspelled, as
the underlying mechanism tried to be as lenient as possible.  The funny
thing was that parsing of "@{now}" even relied on the fact that anything
not recognized by the machinery returned the current timestamp.

Introduce approxidate_careful() that takes an optional pointer to an
integer, that gets assigned 1 when the input does not make sense as a
timestamp.

As I am too lazy to fix all the callers that use approxidate(), most of
the callers do not take advantage of the error checking, but convert the
code to parse reflog to use it as a demonstration.

Tests are mostly from Jeff King.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 35 insertions, 8 deletions

diff --git a/date.c b/date.c
index 5d05ef61cf..17385a9b62 100644
--- a/date.c
+++ b/date.c
@@ -696,6 +696,11 @@ static unsigned long update_tm(struct tm *tm, struct tm *now, unsigned long sec)
 	return n;
 }
 
+static void date_now(struct tm *tm, struct tm *now, int *num)
+{
+	update_tm(tm, now, 0);
+}
+
 static void date_yesterday(struct tm *tm, struct tm *now, int *num)
 {
 	update_tm(tm, now, 24*60*60);
@@ -770,6 +775,7 @@ static const struct special {
 	{ "PM", date_pm },
 	{ "AM", date_am },
 	{ "never", date_never },
+	{ "now", date_now },
 	{ NULL }
 };
 
@@ -790,7 +796,7 @@ static const struct typelen {
 	{ NULL }
 };
 
-static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm *now, int *num)
+static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm *now, int *num, int *touched)
 {
 	const struct typelen *tl;
 	const struct special *s;
@@ -804,6 +810,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 		int match = match_string(date, month_names[i]);
 		if (match >= 3) {
 			tm->tm_mon = i;
+			*touched = 1;
 			return end;
 		}
 	}
@@ -812,6 +819,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 		int len = strlen(s->name);
 		if (match_string(date, s->name) == len) {
 			s->fn(tm, now, num);
+			*touched = 1;
 			return end;
 		}
 	}
@@ -821,11 +829,14 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 			int len = strlen(number_name[i]);
 			if (match_string(date, number_name[i]) == len) {
 				*num = i;
+				*touched = 1;
 				return end;
 			}
 		}
-		if (match_string(date, "last") == 4)
+		if (match_string(date, "last") == 4) {
 			*num = 1;
+			*touched = 1;
+		}
 		return end;
 	}
 
@@ -835,6 +846,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 		if (match_string(date, tl->type) >= len-1) {
 			update_tm(tm, now, tl->length * *num);
 			*num = 0;
+			*touched = 1;
 			return end;
 		}
 		tl++;
@@ -852,6 +864,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 			diff += 7*n;
 
 			update_tm(tm, now, diff * 24 * 60 * 60);
+			*touched = 1;
 			return end;
 		}
 	}
@@ -866,6 +879,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 			tm->tm_year--;
 		}
 		tm->tm_mon = n;
+		*touched = 1;
 		return end;
 	}
 
@@ -873,6 +887,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 		update_tm(tm, now, 0); /* fill in date fields if needed */
 		tm->tm_year -= *num;
 		*num = 0;
+		*touched = 1;
 		return end;
 	}
 
@@ -929,9 +944,12 @@ static void pending_number(struct tm *tm, int *num)
 	}
 }
 
-static unsigned long approxidate_str(const char *date, const struct timeval *tv)
+static unsigned long approxidate_str(const char *date,
+				     const struct timeval *tv,
+				     int *error_ret)
 {
 	int number = 0;
+	int touched = 0;
 	struct tm tm, now;
 	time_t time_sec;
 
@@ -951,33 +969,42 @@ static unsigned long approxidate_str(const char *date, const struct timeval *tv)
 		if (isdigit(c)) {
 			pending_number(&tm, &number);
 			date = approxidate_digit(date-1, &tm, &number);
+			touched = 1;
 			continue;
 		}
 		if (isalpha(c))
-			date = approxidate_alpha(date-1, &tm, &now, &number);
+			date = approxidate_alpha(date-1, &tm, &now, &number, &touched);
 	}
 	pending_number(&tm, &number);
+	if (!touched)
+		*error_ret = 1;
 	return update_tm(&tm, &now, 0);
 }
 
 unsigned long approxidate_relative(const char *date, const struct timeval *tv)
 {
 	char buffer[50];
+	int errors = 0;
 
 	if (parse_date(date, buffer, sizeof(buffer)) > 0)
 		return strtoul(buffer, NULL, 0);
 
-	return approxidate_str(date, tv);
+	return approxidate_str(date, tv, &errors);
 }
 
-unsigned long approxidate(const char *date)
+unsigned long approxidate_careful(const char *date, int *error_ret)
 {
 	struct timeval tv;
 	char buffer[50];
+	int dummy = 0;
+	if (!error_ret)
+		error_ret = &dummy;
 
-	if (parse_date(date, buffer, sizeof(buffer)) > 0)
+	if (parse_date(date, buffer, sizeof(buffer)) > 0) {
+		*error_ret = 0;
 		return strtoul(buffer, NULL, 0);
+	}
 
 	gettimeofday(&tv, NULL);
-	return approxidate_str(date, &tv);
+	return approxidate_str(date, &tv, error_ret);
 }