trace: add trace_vprintf

This is a necessary cleanup to adding new types of trace
functions.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -1067,6 +1067,7 @@ extern void alloc_report(void);
 /* trace.c */
 __attribute__((format (printf, 1, 2)))
 extern void trace_printf(const char *format, ...);
+extern void trace_vprintf(const char *format, va_list ap);
 __attribute__((format (printf, 2, 3)))
 extern void trace_argv_printf(const char **argv, const char *format, ...);
 extern void trace_repo_setup(const char *prefix);

trace.c

@@ -62,28 +62,32 @@ static int get_trace_fd(int *need_close)
 static const char err_msg[] = "Could not trace into fd given by "
 	"GIT_TRACE environment variable";
 
-void trace_printf(const char *fmt, ...)
+void trace_vprintf(const char *fmt, va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
-	va_list ap;
 	int fd, need_close = 0;
 
 	fd = get_trace_fd(&need_close);
 	if (!fd)
 		return;
 
 	set_try_to_free_routine(NULL);	/* is never reset */
-	va_start(ap, fmt);
 	strbuf_vaddf(&buf, fmt, ap);
-	va_end(ap);
-
 	write_or_whine_pipe(fd, buf.buf, buf.len, err_msg);
 	strbuf_release(&buf);
 
 	if (need_close)
 		close(fd);
 }
 
+void trace_printf(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	trace_vprintf(fmt, ap);
+	va_end(ap);
+}
+
 void trace_argv_printf(const char **argv, const char *fmt, ...)
 {
 	struct strbuf buf = STRBUF_INIT;