RFC: dynamic "auto" date formats

[Linus Torvalds <torvalds@linux-foundation.org>]

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This is a throw-away idea with a simple patch attached, which I don't
think anybody should really take all that seriously per se, but I
thought I'd throw it out and see if it generates any discussion.

I almost never use anything but the default date format (DATE_NORMAL),
but every once in a while I will use "--date=relative", typically
because I'm looking at my own commits and I'm just checking when I did
something.

It struck me that I've made the default for most of the logging things
be that when I'm just browsing with the pager, git will automatically
do the right thing. So I have

  [color]
      ui=auto

  [log]
      decorate = auto

in my ~/.gitconfig, and it shows me all those other things I tench to
want to know (like "thar's what I've pushed out" thanks to
decorations).

So I started thinking about when I care about dates, and decided that
maybe I can have a "--date=auto" too. It basically uses relative date
formats for the last 24 hours, and then switches over to the default
format.

I've used it a bit, and like Katy Perry said, I think I might like it.

Note that this doesn't add any gitconfig setting to do this, which
would be part of the whole point if this is actually sensible. But I'm
not entirely convinced it's worth it in the first place, thus this
email to see how people react ("That's just stupid" vs "yeah, I didn't
even know I wanted it, but now I need it").

And no, I'm not at all sure that the 24-hour cut-off is the right
thing, but it didn't seem completely crazy either. I tend to like the
relative date format when it is "19 minutes ago" vs "2 hours ago", at
some point it's long enough ago that it's more useful to know "Tuesday
at 3pm" than about how long ago it was.

(And yes, it would be even better to have the "short term relative
date" turn into a "medium-term 'day of the week at time x'" and then
turn into "full date" when it's more than a week ago, but this patch
only has the two modes of "short term" and "long term" and nothing in
between).

               Linus

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 builtin/blame.c |  1 +
 cache.h         |  3 ++-
 date.c          | 10 +++++++---
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/builtin/blame.c b/builtin/blame.c
index 21f42b0b62b8..4d87181dc6cd 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -2640,6 +2640,7 @@ parse_done:
 		   fewer display columns. */
 		blame_date_width = utf8_strwidth(_("4 years, 11 months ago")) + 1; /* add the null */
 		break;
+	case DATE_AUTO:
 	case DATE_NORMAL:
 		blame_date_width = sizeof("Thu Oct 19 16:00:04 2006 -0700");
 		break;
diff --git a/cache.h b/cache.h
index 6049f8671138..624817c20414 100644
--- a/cache.h
+++ b/cache.h
@@ -1223,7 +1223,8 @@ struct date_mode {
 		DATE_ISO8601_STRICT,
 		DATE_RFC2822,
 		DATE_STRFTIME,
-		DATE_RAW
+		DATE_RAW,
+		DATE_AUTO,
 	} type;
 	const char *strftime_fmt;
 	int local;
diff --git a/date.c b/date.c
index 7c9f76998ac7..c38414a3d968 100644
--- a/date.c
+++ b/date.c
@@ -184,13 +184,15 @@ const char *show_date(unsigned long time, int tz, const struct date_mode *mode)
 		return timebuf.buf;
 	}
 
-	if (mode->type == DATE_RELATIVE) {
+	if (mode->type == DATE_RELATIVE || mode->type == DATE_AUTO) {
 		struct timeval now;
 
 		strbuf_reset(&timebuf);
 		gettimeofday(&now, NULL);
-		show_date_relative(time, tz, &now, &timebuf);
-		return timebuf.buf;
+		if (mode->type != DATE_AUTO || time + 24*60*60 > now.tv_sec) {
+			show_date_relative(time, tz, &now, &timebuf);
+			return timebuf.buf;
+		}
 	}
 
 	tm = time_to_tm(time, tz);
@@ -792,6 +794,8 @@ static enum date_mode_type parse_date_type(const char *format, const char **end)
 		return DATE_RAW;
 	if (skip_prefix(format, "format", end))
 		return DATE_STRFTIME;
+	if (skip_prefix(format, "auto", end))
+		return DATE_AUTO;
 
 	die("unknown date format %s", format);
 }