Subject: Re: [PATCH 2/2] date: make "local" orthogonal to date format

From: John Keeping <[email-masked]>
Date: Mon, 31 Aug 2015 22:27:54 +0100

On Mon, Aug 31, 2015 at 04:48:32PM -0400, Jeff King wrote:
> Most of our "--date" modes are about the format of the date:
> which items we show and in what order. But "--date=local" is
> a bit of an oddball. It means "show the date in the normal
> format, but using the local timezone". The timezone we use
> is orthogonal to the actual format, and there is no reason
> we could not have "localized iso8601", etc.
> 
> This patch adds a "local" boolean field to "struct
> date_mode", and drops the DATE_LOCAL element from the
> date_mode_type enum (it's now just DATE_NORMAL plus
> local=1). The new feature is accessible to users by adding
> "-local" to any date mode (e.g., "iso-local"), and we retain
> "local" as an alias for "default-local" for backwards
> compatibility.
> 
> Signed-off-by: Jeff King <[email-masked]>
> ---

This fails t6300 with:

fatal: unknown date-mode modifier: my date is %Y-%m-%d
not ok 83 - Check format of strftime date fields
#
#               echo "my date is 2006-07-03" >expected &&
#               git for-each-ref \
#                 --format="%(authordate:format:my date is %Y-%m-%d)" \
#                 refs/heads >actual &&
#               test_cmp expected actual
#

The following squash-in fixes it:

diff --git a/date.c b/date.c
index aa57cad..3aa8002 100644
--- a/date.c
+++ b/date.c
@@ -817,9 +817,7 @@ void parse_date_format(const char *format, struct date_mode *mode)
 		if (!skip_prefix(p, ":", &p))
 			die("date format missing colon separator: %s", format);
 		mode->strftime_fmt = xstrdup(p);
-	}
-
-	if (*p)
+	} else if (*p)
 		die("unknown date-mode modifier: %s", p);
 }

> I wonder if anybody would be confused and try "iso-local-strict", which
> does not work with this code. If we bumped "-strict" to become a
> modifier (like "-local"), we could easily make the order
> interchangeable.
> 
>  Documentation/rev-list-options.txt | 21 ++++++++---
>  builtin/blame.c                    |  1 -
>  cache.h                            |  2 +-
>  date.c                             | 77 +++++++++++++++++++++++++-------------
>  4 files changed, 67 insertions(+), 34 deletions(-)
> 
> diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
> index a9b808f..35dc44b 100644
> --- a/Documentation/rev-list-options.txt
> +++ b/Documentation/rev-list-options.txt
> @@ -702,12 +702,16 @@ include::pretty-options.txt[]
>  --date=(relative|local|default|iso|iso-strict|rfc|short|raw)::
>  	Only takes effect for dates shown in human-readable format, such
>  	as when using `--pretty`. `log.date` config variable sets a default
> -	value for the log command's `--date` option.
> +	value for the log command's `--date` option. By default, dates
> +	are shown in the original time zone (either committer's or
> +	author's). If `-local` is appended to the format (e.g.,
> +	`iso-local`), the user's local time zone is used instead.
>  +
>  `--date=relative` shows dates relative to the current time,
> -e.g. ``2 hours ago''.
> +e.g. ``2 hours ago''. The `-local` option cannot be used with
> +`--relative`.
>  +
> -`--date=local` shows timestamps in user's local time zone.
> +`--date=local` is an alias for `--date=default-local`.
>  +
>  `--date=iso` (or `--date=iso8601`) shows timestamps in a ISO 8601-like format.
>  The differences to the strict ISO 8601 format are:
> @@ -730,10 +734,15 @@ format, often found in email messages.
>  `--date=format:...` feeds the format `...` to your system `strftime`.
>  Use `--date=format:%c` to show the date in your system locale's
>  preferred format.  See the `strftime` manual for a complete list of
> -format placeholders.
> +format placeholders. When using `-local`, the correct syntax is
> +`--date=format-local:...`.
>  +
> -`--date=default` shows timestamps in the original time zone
> -(either committer's or author's).
> +`--date=default` is the default format, and is similar to
> +`--date=rfc2822`, with a few exceptions:
> +
> +	- there is no comma after the day-of-week
> +
> +	- the time zone is omitted when the local time zone is used
>  
>  ifdef::git-rev-list[]
>  --header::
> diff --git a/builtin/blame.c b/builtin/blame.c
> index 4db01c1..6fd1a63 100644
> --- a/builtin/blame.c
> +++ b/builtin/blame.c
> @@ -2600,7 +2600,6 @@ parse_done:
>  		   fewer display columns. */
>  		blame_date_width = utf8_strwidth(_("4 years, 11 months ago")) + 1; /* add the null */
>  		break;
> -	case DATE_LOCAL:
>  	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 4e25271..9a91b1d 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -1091,7 +1091,6 @@ struct date_mode {
>  		DATE_NORMAL = 0,
>  		DATE_RELATIVE,
>  		DATE_SHORT,
> -		DATE_LOCAL,
>  		DATE_ISO8601,
>  		DATE_ISO8601_STRICT,
>  		DATE_RFC2822,
> @@ -1099,6 +1098,7 @@ struct date_mode {
>  		DATE_RAW
>  	} type;
>  	const char *strftime_fmt;
> +	int local;
>  };
>  
>  /*
> diff --git a/date.c b/date.c
> index 8f91569..aa57cad 100644
> --- a/date.c
> +++ b/date.c
> @@ -166,6 +166,7 @@ struct date_mode *date_mode_from_type(enum date_mode_type type)
>  	if (type == DATE_STRFTIME)
>  		die("BUG: cannot create anonymous strftime date_mode struct");
>  	mode.type = type;
> +	mode.local = 0;
>  	return &mode;
>  }
>  
> @@ -189,7 +190,7 @@ const char *show_date(unsigned long time, int tz, const struct date_mode *mode)
>  		return timebuf.buf;
>  	}
>  
> -	if (mode->type == DATE_LOCAL)
> +	if (mode->local)
>  		tz = local_tzoffset(time);
>  
>  	tm = time_to_tm(time, tz);
> @@ -232,7 +233,7 @@ const char *show_date(unsigned long time, int tz, const struct date_mode *mode)
>  				tm->tm_mday,
>  				tm->tm_hour, tm->tm_min, tm->tm_sec,
>  				tm->tm_year + 1900,
> -				(mode->type == DATE_LOCAL) ? 0 : ' ',
> +				mode->local ? 0 : ' ',
>  				tz);
>  	return timebuf.buf;
>  }
> @@ -770,32 +771,56 @@ int parse_date(const char *date, struct strbuf *result)
>  	return 0;
>  }
>  
> +static enum date_mode_type parse_date_type(const char *format, const char **end)
> +{
> +	if (skip_prefix(format, "relative", end))
> +		return DATE_RELATIVE;
> +	if (skip_prefix(format, "iso8601-strict", end) ||
> +	    skip_prefix(format, "iso-strict", end))
> +		return DATE_ISO8601_STRICT;
> +	if (skip_prefix(format, "iso8601", end) ||
> +	    skip_prefix(format, "iso", end))
> +		return DATE_ISO8601;
> +	if (skip_prefix(format, "rfc2822", end) ||
> +	    skip_prefix(format, "rfc", end))
> +		return DATE_RFC2822;
> +	if (skip_prefix(format, "short", end))
> +		return DATE_SHORT;
> +	if (skip_prefix(format, "default", end))
> +		return DATE_NORMAL;
> +	if (skip_prefix(format, "raw", end))
> +		return DATE_RAW;
> +	if (skip_prefix(format, "format", end))
> +		return DATE_STRFTIME;
> +
> +	die("unknown date format %s", format);
> +}
> +
>  void parse_date_format(const char *format, struct date_mode *mode)
>  {
> -	if (!strcmp(format, "relative"))
> -		mode->type = DATE_RELATIVE;
> -	else if (!strcmp(format, "iso8601") ||
> -		 !strcmp(format, "iso"))
> -		mode->type = DATE_ISO8601;
> -	else if (!strcmp(format, "iso8601-strict") ||
> -		 !strcmp(format, "iso-strict"))
> -		mode->type = DATE_ISO8601_STRICT;
> -	else if (!strcmp(format, "rfc2822") ||
> -		 !strcmp(format, "rfc"))
> -		mode->type = DATE_RFC2822;
> -	else if (!strcmp(format, "short"))
> -		mode->type = DATE_SHORT;
> -	else if (!strcmp(format, "local"))
> -		mode->type = DATE_LOCAL;
> -	else if (!strcmp(format, "default"))
> -		mode->type = DATE_NORMAL;
> -	else if (!strcmp(format, "raw"))
> -		mode->type = DATE_RAW;
> -	else if (skip_prefix(format, "format:", &format)) {
> -		mode->type = DATE_STRFTIME;
> -		mode->strftime_fmt = xstrdup(format);
> -	} else
> -		die("unknown date format %s", format);
> +	const char *p;
> +
> +	/* historical alias */
> +	if (!strcmp(format, "local"))
> +		format = "default-local";
> +
> +	mode->type = parse_date_type(format, &p);
> +	mode->local = 0;
> +
> +	if (skip_prefix(p, "-local", &p)) {
> +		if (mode->type == DATE_RELATIVE)
> +			die("relative-local date format is nonsensical");
> +		mode->local = 1;
> +	}
> +
> +	if (mode->type == DATE_STRFTIME) {
> +		if (!skip_prefix(p, ":", &p))
> +			die("date format missing colon separator: %s", format);
> +		mode->strftime_fmt = xstrdup(p);
> +	}
> +
> +	if (*p)
> +		die("unknown date-mode modifier: %s", p);
>  }
>  
>  void datestamp(struct strbuf *out)
> -- 
> 2.5.1.739.g7891f6b