date.c: allow ISO 8601 reduced precision times

ISO 8601 permits "reduced precision" time representations to omit the
seconds value or both the minutes and the seconds values.  The
abbreviate times could look like 17:45 or 1745 to omit the seconds,
or simply as 17 to omit both the minutes and the seconds.

parse_date_basic accepts the 17:45 format but it rejects the other two.
Change it to accept 4-digit and 2-digit time values when they follow a
recognized date and a 'T'.

Before this change:

$ TZ=UTC test-tool date approxidate 2022-12-13T23:00 2022-12-13T2300 2022-12-13T23
2022-12-13T23:00 -> 2022-12-13 23:00:00 +0000
2022-12-13T2300 -> 2022-12-13 23:54:13 +0000
2022-12-13T23 -> 2022-12-13 23:54:13 +0000

After this change:

$ TZ=UTC helper/test-tool date approxidate 2022-12-13T23:00 2022-12-13T2300 2022-12-13T23
2022-12-13T23:00 -> 2022-12-13 23:00:00 +0000
2022-12-13T2300 -> 2022-12-13 23:00:00 +0000
2022-12-13T23 -> 2022-12-13 23:00:00 +0000

Note: ISO 8601 also allows reduced precision date strings such as
"2022-12" and "2022". This patch does not attempt to address these.

Reported-by: Pat LaVarre <plavarre@purestorage.com>
Signed-off-by: Phil Hord <phil.hord@gmail.com>
Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/date.c b/date.c
index 53bd6a7932e3279fe0338c464efeef4416181fee..6f45eeb3568671e5b4bb37c2830315a490a12cfe 100644 (file)
--- a/date.c
+++ b/date.c
@@ -493,6 +493,12 @@ static int match_alpha(const char *date, struct tm *tm, int *offset)
                return 2;
        }
 
+       /* ISO-8601 allows yyyymmDD'T'HHMMSS, with less precision */
+       if (*date == 'T' && isdigit(date[1]) && tm->tm_hour == -1) {
+               tm->tm_min = tm->tm_sec = 0;
+               return 1;
+       }
+
        /* BAD CRAP */
        return skip_alpha(date);
 }
@@ -638,6 +644,18 @@ static inline int nodate(struct tm *tm)
                tm->tm_sec) < 0;
 }
 
+/*
+ * Have we seen an ISO-8601-alike date, i.e. 20220101T0,
+ * In which, hour is still unset,
+ * and minutes and second has been set to 0.
+ */
+static inline int maybeiso8601(struct tm *tm)
+{
+       return tm->tm_hour == -1 &&
+               tm->tm_min == 0 &&
+               tm->tm_sec == 0;
+}
+
 /*
  * We've seen a digit. Time? Year? Date?
  */
@@ -701,6 +719,25 @@ static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
                return end - date;
        }
 
+       /* reduced precision of ISO-8601's time: HHMM or HH */
+       if (maybeiso8601(tm)) {
+               unsigned int num1 = num;
+               unsigned int num2 = 0;
+               if (n == 4) {
+                       num1 = num / 100;
+                       num2 = num % 100;
+               }
+               if ((n == 4 || n == 2) && !nodate(tm) &&
+                   set_time(num1, num2, 0, tm) == 0)
+                       return n;
+               /*
+                * We thought this is an ISO-8601 time string,
+                * we set minutes and seconds to 0,
+                * turn out it isn't, rollback the change.
+                */
+               tm->tm_min = tm->tm_sec = -1;
+       }
+
        /* Four-digit year or a timezone? */
        if (n == 4) {
                if (num <= 1400 && *offset == -1) {

diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 2490162071e700e8a69d0e6311b6f22eda4e7046..e18b1602864ec432553266e89d3796e94741e8e0 100755 (executable)
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -88,6 +88,13 @@ check_parse 2008-02-14 bad
 check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 +0000'
 check_parse '2008-02-14 20:30:45 -0500' '2008-02-14 20:30:45 -0500'
 check_parse '2008.02.14 20:30:45 -0500' '2008-02-14 20:30:45 -0500'
+check_parse '20080214T20:30:45' '2008-02-14 20:30:45 +0000'
+check_parse '20080214T20:30' '2008-02-14 20:30:00 +0000'
+check_parse '20080214T20' '2008-02-14 20:00:00 +0000'
+check_parse '20080214T203045' '2008-02-14 20:30:45 +0000'
+check_parse '20080214T2030' '2008-02-14 20:30:00 +0000'
+check_parse '20080214T000000.20' '2008-02-14 00:00:00 +0000'
+check_parse '20080214T00:00:00.20' '2008-02-14 00:00:00 +0000'
 check_parse '20080214T203045-04:00' '2008-02-14 20:30:45 -0400'
 check_parse '20080214T203045 -04:00' '2008-02-14 20:30:45 -0400'
 check_parse '20080214T203045.019-04:00' '2008-02-14 20:30:45 -0400'
@@ -99,6 +106,7 @@ check_parse '2008-02-14 20:30:45 -05' '2008-02-14 20:30:45 -0500'
 check_parse '2008-02-14 20:30:45 -:30' '2008-02-14 20:30:45 +0000'
 check_parse '2008-02-14 20:30:45 -05:00' '2008-02-14 20:30:45 -0500'
 check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 -0500' EST5
+check_parse 'Thu, 7 Apr 2005 15:14:13 -0700' '2005-04-07 15:14:13 -0700'
 
 check_approxidate() {
        echo "$1 -> $2 +0000" >expect