date API: provide and use a DATE_MODE_INIT

Provide and use a DATE_MODE_INIT macro. Most of the users of struct
date_mode" use it via pretty.h's "struct pretty_print_context" which
doesn't have an initialization macro, so we're still bound to being
initialized to "{ 0 }" by default.

But we can change the couple of callers that directly declared a
variable on the stack to instead use the initializer, and thus do away
with the "mode.local = 0" added in add00ba2de (date: make "local"
orthogonal to date format, 2015-09-03).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

date.c

@@ -206,11 +206,10 @@ void show_date_relative(timestamp_t time, struct strbuf *timebuf)
 
 struct date_mode *date_mode_from_type(enum date_mode_type type)
 {
-	static struct date_mode mode;
+	static struct date_mode mode = DATE_MODE_INIT;
 	if (type == DATE_STRFTIME)
 		BUG("cannot create anonymous strftime date_mode struct");
 	mode.type = type;
-	mode.local = 0;
 	return &mode;
 }
 

date.h

@@ -20,6 +20,10 @@ struct date_mode {
 	int local;
 };
 
+#define DATE_MODE_INIT { \
+	.type = DATE_NORMAL, \
+}
+
 /*
  * Convenience helper for passing a constant type, like:
  *

ref-filter.c

@@ -1251,7 +1251,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	char *zone;
 	timestamp_t timestamp;
 	long tz;
-	struct date_mode date_mode = { DATE_NORMAL };
+	struct date_mode date_mode = DATE_MODE_INIT;
 	const char *formatp;
 
 	/*

t/helper/test-date.c

@@ -35,7 +35,7 @@ static void show_human_dates(const char **argv)
 
 static void show_dates(const char **argv, const char *format)
 {
-	struct date_mode mode;
+	struct date_mode mode = DATE_MODE_INIT;
 
 	parse_date_format(format, &mode);
 	for (; *argv; argv++) {