advice: extract vadvise() from advise()

In preparation for a new advice method, extract a version of advise()
that uses an explict 'va_list' parameter. Call it from advise() for a
functionally equivalent version.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Heba Waly <heba.waly@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

advice.c

@@ -96,15 +96,12 @@ static struct {
 	{ "pushNonFastForward", &advice_push_update_rejected }
 };
 
-void advise(const char *advice, ...)
+static void vadvise(const char *advice, va_list params)
 {
 	struct strbuf buf = STRBUF_INIT;
-	va_list params;
 	const char *cp, *np;
 
-	va_start(params, advice);
 	strbuf_vaddf(&buf, advice, params);
-	va_end(params);
 
 	for (cp = buf.buf; *cp; cp = np) {
 		np = strchrnul(cp, '\n');
@@ -118,6 +115,14 @@ void advise(const char *advice, ...)
 	strbuf_release(&buf);
 }
 
+void advise(const char *advice, ...)
+{
+	va_list params;
+	va_start(params, advice);
+	vadvise(advice, params);
+	va_end(params);
+}
+
 int git_default_advice_config(const char *var, const char *value)
 {
 	const char *k, *slot_name;