__attribute__: trace2_region_enter_printf() is like "printf"

The last part of the parameter list the function takes is like
parameters to printf.  Mark it as such.

An existing call that formats a value of type size_t using "%d" was
found by the compiler with the help with this annotation; fix it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

run-command.c

@@ -1753,7 +1753,8 @@ void run_processes_parallel(const struct run_process_parallel_opts *opts)
 
 	if (do_trace2)
 		trace2_region_enter_printf(tr2_category, tr2_label, NULL,
-					   "max:%d", opts->processes);
+					   "max:%"PRIuMAX,
+					   (uintmax_t)opts->processes);
 
 	pp_init(&pp, opts, &pp_sig);
 	while (1) {

trace2.h

@@ -390,6 +390,7 @@ void trace2_region_enter_printf_va_fl(const char *file, int line,
 	trace2_region_enter_printf_va_fl(__FILE__, __LINE__, (category), \
 					 (label), (repo), (fmt), (ap))
 
+__attribute__((format (printf, 6, 7)))
 void trace2_region_enter_printf_fl(const char *file, int line,
 				   const char *category, const char *label,
 				   const struct repository *repo,