[PATCH v3] pretty: add --date=iso-strict, a strict ISO-8601 date format

[Beat Bolli <bbolli@ewanet.ch>]

There has been concern that Git's "ISO" date format does not really
conform to the ISO-8601 standard. Thus, it cannot be parsed by ISO-8601
compliant parsers, e.g. those of XML toolchains.

The --date=iso format Git uses deviates from ISO-8601 in these ways:
  - a space instead of the "T" date/time delimiter
  - a space between time and time zone
  - no colon between hours and minutes of the time zone

Add a strict ISO-8601 date format for displaying committer and author
dates. Use the '%aI' and '%cI' format specifiers (note the uppercase
'I') and the '--date=iso-strict' or '--date=iso8601-strict' date format
names.

See http://thread.gmane.org/gmane.comp.version-control.git/255879 and
http://thread.gmane.org/gmane.comp.version-control.git/52414/focus=52585
for discussion.

Signed-off-by: Beat Bolli <bbolli@ewanet.ch>
---

v3:
  - Improve the commit message
  - Add the new format in builtin/blame.c

v2:
  - Improve the commit message
  - Fix time zone display for negative values close to zero

 Documentation/git-rev-list.txt     |  2 +-
 Documentation/pretty-formats.txt   |  6 ++++--
 Documentation/rev-list-options.txt | 13 +++++++++++--
 builtin/blame.c                    |  3 +++
 cache.h                            |  1 +
 date.c                             | 14 +++++++++++++-
 pretty.c                           |  5 ++++-
 t/t4205-log-pretty-formats.sh      |  7 +++++++
 8 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-rev-list.txt b/Documentation/git-rev-list.txt
index 7a1585d..fd7f8b5 100644
--- a/Documentation/git-rev-list.txt
+++ b/Documentation/git-rev-list.txt
@@ -45,7 +45,7 @@ SYNOPSIS
 	     [ \--regexp-ignore-case | -i ]
 	     [ \--extended-regexp | -E ]
 	     [ \--fixed-strings | -F ]
-	     [ \--date=(local|relative|default|iso|rfc|short) ]
+	     [ \--date=(local|relative|default|iso|iso-strict|rfc|short) ]
 	     [ [\--objects | \--objects-edge] [ \--unpacked ] ]
 	     [ \--pretty | \--header ]
 	     [ \--bisect ]
diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 85d6353..50a2c30 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -115,7 +115,8 @@ The placeholders are:
 - '%aD': author date, RFC2822 style
 - '%ar': author date, relative
 - '%at': author date, UNIX timestamp
-- '%ai': author date, ISO 8601 format
+- '%ai': author date, ISO 8601-like format
+- '%aI': author date, strict ISO 8601 format
 - '%cn': committer name
 - '%cN': committer name (respecting .mailmap, see
   linkgit:git-shortlog[1] or linkgit:git-blame[1])
@@ -126,7 +127,8 @@ The placeholders are:
 - '%cD': committer date, RFC2822 style
 - '%cr': committer date, relative
 - '%ct': committer date, UNIX timestamp
-- '%ci': committer date, ISO 8601 format
+- '%ci': committer date, ISO 8601-like format
+- '%cI': committer date, strict ISO 8601 format
 - '%d': ref names, like the --decorate option of linkgit:git-log[1]
 - '%e': encoding
 - '%s': subject
diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index deb8cca..5d311b8 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -677,7 +677,7 @@ include::pretty-options.txt[]
 --relative-date::
 	Synonym for `--date=relative`.
 
---date=(relative|local|default|iso|rfc|short|raw)::
+--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.
@@ -687,7 +687,16 @@ e.g. ``2 hours ago''.
 +
 `--date=local` shows timestamps in user's local time zone.
 +
-`--date=iso` (or `--date=iso8601`) shows timestamps in ISO 8601 format.
+`--date=iso` (or `--date=iso8601`) shows timestamps in a ISO 8601-like format.
+The differences to the strict ISO 8601 format are:
+
+	- a space instead of the `T` date/time delimiter
+	- a space between time and time zone
+	- no colon between hours and minutes of the time zone
+
++
+`--date=iso-strict` (or `--date=iso8601-strict`) shows timestamps in strict
+ISO 8601 format.
 +
 `--date=rfc` (or `--date=rfc2822`) shows timestamps in RFC 2822
 format, often found in email messages.
diff --git a/builtin/blame.c b/builtin/blame.c
index 17d30d0..4f974aa 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -2583,6 +2583,9 @@ parse_done:
 	case DATE_ISO8601:
 		blame_date_width = sizeof("2006-10-19 16:00:04 -0700");
 		break;
+	case DATE_ISO8601_STRICT:
+		blame_date_width = sizeof("2006-10-19T16:00:04-07:00");
+		break;
 	case DATE_RAW:
 		blame_date_width = sizeof("1161298804 -0700");
 		break;
diff --git a/cache.h b/cache.h
index fcb511d..fa92aaf 100644
--- a/cache.h
+++ b/cache.h
@@ -1037,6 +1037,7 @@ enum date_mode {
 	DATE_SHORT,
 	DATE_LOCAL,
 	DATE_ISO8601,
+	DATE_ISO8601_STRICT,
 	DATE_RFC2822,
 	DATE_RAW
 };
diff --git a/date.c b/date.c
index 782de95..5d73d9b 100644
--- a/date.c
+++ b/date.c
@@ -200,7 +200,16 @@ const char *show_date(unsigned long time, int tz, enum date_mode mode)
 				tm->tm_mday,
 				tm->tm_hour, tm->tm_min, tm->tm_sec,
 				tz);
-	else if (mode == DATE_RFC2822)
+	else if (mode == DATE_ISO8601_STRICT) {
+		char sign = (tz >= 0) ? '+' : '-';
+		tz = abs(tz);
+		strbuf_addf(&timebuf, "%04d-%02d-%02dT%02d:%02d:%02d%c%02d:%02d",
+				tm->tm_year + 1900,
+				tm->tm_mon + 1,
+				tm->tm_mday,
+				tm->tm_hour, tm->tm_min, tm->tm_sec,
+				sign, tz / 100, tz % 100);
+	} else if (mode == DATE_RFC2822)
 		strbuf_addf(&timebuf, "%.3s, %d %.3s %d %02d:%02d:%02d %+05d",
 			weekday_names[tm->tm_wday], tm->tm_mday,
 			month_names[tm->tm_mon], tm->tm_year + 1900,
@@ -751,6 +760,9 @@ enum date_mode parse_date_format(const char *format)
 	else if (!strcmp(format, "iso8601") ||
 		 !strcmp(format, "iso"))
 		return DATE_ISO8601;
+	else if (!strcmp(format, "iso8601-strict") ||
+		 !strcmp(format, "iso-strict"))
+		return DATE_ISO8601_STRICT;
 	else if (!strcmp(format, "rfc2822") ||
 		 !strcmp(format, "rfc"))
 		return DATE_RFC2822;
diff --git a/pretty.c b/pretty.c
index 3a1da6f..7dd5601 100644
--- a/pretty.c
+++ b/pretty.c
@@ -731,9 +731,12 @@ static size_t format_person_part(struct strbuf *sb, char part,
 	case 'r':	/* date, relative */
 		strbuf_addstr(sb, show_ident_date(&s, DATE_RELATIVE));
 		return placeholder_len;
-	case 'i':	/* date, ISO 8601 */
+	case 'i':	/* date, ISO 8601-like */
 		strbuf_addstr(sb, show_ident_date(&s, DATE_ISO8601));
 		return placeholder_len;
+	case 'I':	/* date, ISO 8601 strict */
+		strbuf_addstr(sb, show_ident_date(&s, DATE_ISO8601_STRICT));
+		return placeholder_len;
 	}
 
 skip:
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 349c531..aad7a80 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -431,6 +431,13 @@ EOF
 	test_cmp expected actual
 '
 
+# ISO strict date format
+test_expect_success 'ISO and ISO-strict date formats display the same values' '
+	git log --format=%ai%n%ci | sed -e "s/ /T/; s/ //; s/..\$/:&/" >expected &&
+	git log --format=%aI%n%cI >actual &&
+	test_cmp expected actual
+'
+
 # get new digests (with no abbreviations)
 head1=$(git rev-parse --verify HEAD~0) &&
 head2=$(git rev-parse --verify HEAD~1) &&
-- 
2.1.0