Merge branch 'rs/strbuf-addftime-zZ'

As there is no portable way to pass timezone information to
strftime, some output format from "git log" and friends are
impossible to produce.  Teach our own strbuf_addftime to replace %z
and %Z with caller-supplied values to help working around this.

* rs/strbuf-addftime-zZ:
  date: use localtime() for "-local" time formats
  t0006: check --date=format zone offsets
  strbuf: let strbuf_addftime handle %z and %Z itself

5 files changed, 73 insertions, 11 deletions

diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index 9c44eae55d..a6cf9eb380 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -769,7 +769,8 @@ timezone value.
 1970).  As with `--raw`, this is always in UTC and therefore `-local`
 has no effect.
 +
-`--date=format:...` feeds the format `...` to your system `strftime`.
+`--date=format:...` feeds the format `...` to your system `strftime`,
+except for %z and %Z, which are handled internally.
 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. When using `-local`, the correct syntax is
diff --git a/date.c b/date.c
index 63fa99685e..1fd6d66375 100644
--- a/date.c
+++ b/date.c
@@ -70,6 +70,12 @@ static struct tm *time_to_tm(timestamp_t time, int tz)
 	return gmtime(&t);
 }
 
+static struct tm *time_to_tm_local(timestamp_t time)
+{
+	time_t t = time;
+	return localtime(&t);
+}
+
 /*
  * What value of "tz" was in effect back then at "time" in the
  * local timezone?
@@ -214,7 +220,10 @@ const char *show_date(timestamp_t time, int tz, const struct date_mode *mode)
 		return timebuf.buf;
 	}
 
-	tm = time_to_tm(time, tz);
+	if (mode->local)
+		tm = time_to_tm_local(time);
+	else
+		tm = time_to_tm(time, tz);
 	if (!tm) {
 		tm = time_to_tm(0, 0);
 		tz = 0;
@@ -246,7 +255,8 @@ const char *show_date(timestamp_t time, int tz, const struct date_mode *mode)
 			month_names[tm->tm_mon], tm->tm_year + 1900,
 			tm->tm_hour, tm->tm_min, tm->tm_sec, tz);
 	else if (mode->type == DATE_STRFTIME)
-		strbuf_addftime(&timebuf, mode->strftime_fmt, tm);
+		strbuf_addftime(&timebuf, mode->strftime_fmt, tm, tz,
+				mode->local ? NULL : "");
 	else
 		strbuf_addf(&timebuf, "%.3s %.3s %d %02d:%02d:%02d %d%c%+05d",
 				weekday_names[tm->tm_wday],
diff --git a/strbuf.c b/strbuf.c
index 00457940cf..be3b9e37b1 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -785,14 +785,48 @@ char *xstrfmt(const char *fmt, ...)
 	return ret;
 }
 
-void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
+void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm,
+		     int tz_offset, const char *tz_name)
 {
+	struct strbuf munged_fmt = STRBUF_INIT;
 	size_t hint = 128;
 	size_t len;
 
 	if (!*fmt)
 		return;
 
+	/*
+	 * There is no portable way to pass timezone information to
+	 * strftime, so we handle %z and %Z here.
+	 */
+	for (;;) {
+		const char *percent = strchrnul(fmt, '%');
+		strbuf_add(&munged_fmt, fmt, percent - fmt);
+		if (!*percent)
+			break;
+		fmt = percent + 1;
+		switch (*fmt) {
+		case '%':
+			strbuf_addstr(&munged_fmt, "%%");
+			fmt++;
+			break;
+		case 'z':
+			strbuf_addf(&munged_fmt, "%+05d", tz_offset);
+			fmt++;
+			break;
+		case 'Z':
+			if (tz_name) {
+				strbuf_addstr(&munged_fmt, tz_name);
+				fmt++;
+				break;
+			}
+			/* FALLTHROUGH */
+		default:
+			strbuf_addch(&munged_fmt, '%');
+		}
+	}
+	fmt = munged_fmt.buf;
+
 	strbuf_grow(sb, hint);
 	len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm);
 
@@ -804,17 +838,16 @@ void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
 		 * output contains at least one character, and then drop the extra
 		 * character before returning.
 		 */
-		struct strbuf munged_fmt = STRBUF_INIT;
-		strbuf_addf(&munged_fmt, "%s ", fmt);
+		strbuf_addch(&munged_fmt, ' ');
 		while (!len) {
 			hint *= 2;
 			strbuf_grow(sb, hint);
 			len = strftime(sb->buf + sb->len, sb->alloc - sb->len,
 				       munged_fmt.buf, tm);
 		}
-		strbuf_release(&munged_fmt);
 		len--; /* drop munged space */
 	}
+	strbuf_release(&munged_fmt);
 	strbuf_setlen(sb, sb->len + len);
 }
 
diff --git a/strbuf.h b/strbuf.h
index 80047b1bb7..4559035c47 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -340,8 +340,14 @@ extern void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap);
 
 /**
  * Add the time specified by `tm`, as formatted by `strftime`.
- */
-extern void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm);
+ * `tz_name` is used to expand %Z internally unless it's NULL.
+ * `tz_offset` is in decimal hhmm format, e.g. -600 means six hours west
+ * of Greenwich, and it's used to expand %z internally.  However, tokens
+ * with modifiers (e.g. %Ez) are passed to `strftime`.
+ */
+extern void strbuf_addftime(struct strbuf *sb, const char *fmt,
+			    const struct tm *tm, int tz_offset,
+			    const char *tz_name);
 
 /**
  * Read a given size of data from a FILE* pointer to the buffer.
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 42d4ea61ef..7ac9466d50 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -31,9 +31,11 @@ check_show () {
 	format=$1
 	time=$2
 	expect=$3
-	test_expect_success $4 "show date ($format:$time)" '
+	prereqs=$4
+	zone=$5
+	test_expect_success $prereqs "show date ($format:$time)" '
 		echo "$time -> $expect" >expect &&
-		test-date show:$format "$time" >actual &&
+		TZ=${zone:-$TZ} test-date show:"$format" "$time" >actual &&
 		test_cmp expect actual
 	'
 }
@@ -51,6 +53,16 @@ check_show iso-local "$TIME" '2016-06-15 14:13:20 +0000'
 check_show raw-local "$TIME" '1466000000 +0000'
 check_show unix-local "$TIME" '1466000000'
 
+check_show 'format:%z' "$TIME" '+0200'
+check_show 'format-local:%z' "$TIME" '+0000'
+check_show 'format:%Z' "$TIME" ''
+check_show 'format-local:%Z' "$TIME" 'UTC'
+check_show 'format:%%z' "$TIME" '%z'
+check_show 'format-local:%%z' "$TIME" '%z'
+
+check_show 'format:%Y-%m-%d %H:%M:%S' "$TIME" '2016-06-15 16:13:20'
+check_show 'format-local:%Y-%m-%d %H:%M:%S' "$TIME" '2016-06-15 09:13:20' '' EST5
+
 # arbitrary time absurdly far in the future
 FUTURE="5758122296 -0400"
 check_show iso       "$FUTURE" "2152-06-19 18:24:56 -0400" TIME_IS_64BIT,TIME_T_IS_64BIT