[RFC PATCH] approxidate: make "today" wrap to midnight

[Tuomas Ahola <taahol@utu.fi>]

Although some commands do reject invalid approxidate expressions,
in other cases those are simply evaluated as the current time.
Oftentimes that is a perfectly good compromise to handle silly
requests, but it isn't without rough edges.

Let's consider what "git log --since=today" should yield.
As it happens that "today" isn't actually a valid approxidate
format, the command currently tries to list commits with
*future* timestamps.  Perhaps it would make more sense if
it returned the commits made since midnight---that is,
during the current day.

Moreover, a revision parameter "@{today}" is currently outright
rejected.  Making "today" a valid approxidate time format could
make a natural way to specify the state of the ref at the start
of the current day.

Bind "today" to new function `date_today()` as an approxidate
special.  Make it return the last midnight if no specific time
is given; i.e. retain the old behavior of "noon today" and such.

Signed-off-by: Tuomas Ahola <taahol@utu.fi>
---

Notes:
    The "Jan 5 today" test is adapted from
    
      c27cc94fad (approxidate: handle pending number for "specials", 2018-11-02):
    
    > (saying "Jan 5 yesterday" should not respect the number at all).

 date.c          | 10 ++++++++++
 t/t0006-date.sh |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/date.c b/date.c
index 17a95077cf..343d6aab6f 100644
--- a/date.c
+++ b/date.c
@@ -1192,6 +1192,15 @@ static void date_never(struct tm *tm, struct tm *now UNUSED, int *num)
 	*num = 0;
 }
 
+static void date_today(struct tm *tm, struct tm *now, int *num UNUSED)
+{
+	if (tm->tm_hour == now->tm_hour &&
+	    tm->tm_min == now->tm_min &&
+	    tm->tm_sec == now->tm_sec)
+		date_time(tm, now, 0);
+	update_tm(tm, now, 0);
+}
+
 static const struct special {
 	const char *name;
 	void (*fn)(struct tm *, struct tm *, int *);
@@ -1204,6 +1213,7 @@ static const struct special {
 	{ "AM", date_am },
 	{ "never", date_never },
 	{ "now", date_now },
+	{ "today", date_today },
 	{ NULL }
 };
 
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 53ced36df4..07bf6115ab 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -164,6 +164,7 @@ check_approxidate() {
 }
 
 check_approxidate now '2009-08-30 19:20:00'
+check_approxidate today '2009-08-30 00:00:00'
 check_approxidate '5 seconds ago' '2009-08-30 19:19:55'
 check_approxidate 5.seconds.ago '2009-08-30 19:19:55'
 check_approxidate 10.minutes.ago '2009-08-30 19:10:00'
@@ -187,6 +188,7 @@ check_approxidate 'last tuesday' '2009-08-25 19:20:00'
 check_approxidate 'July 5th' '2009-07-05 19:20:00'
 check_approxidate '06/05/2009' '2009-06-05 19:20:00'
 check_approxidate '06.05.2009' '2009-05-06 19:20:00'
+check_approxidate 'Jan 5 today' '2009-01-30 00:00:00'
 
 check_approxidate 'Jun 6, 5AM' '2009-06-06 05:00:00'
 check_approxidate '5AM Jun 6' '2009-06-06 05:00:00'

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
2.30.2