__attribute__: add a few missing format attributes

A public function mem_pool_strfmt() takes printf like parameters,
but is not given an attribute as such.  Also a few file-scope static
functions were missing their format attribute.

Add them.

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

Author: gitster

mem-pool.h

@@ -50,6 +50,7 @@ char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len);
 /*
  * Allocate memory from the memory pool and format a string into it.
  */
+__attribute__((format (printf, 2, 3)))
 char *mem_pool_strfmt(struct mem_pool *pool, const char *fmt, ...);
 
 /*

scalar.c

@@ -289,6 +289,7 @@ static int unregister_dir(void)
 }
 
 /* printf-style interface, expects `<key>=<value>` argument */
+__attribute__((format (printf, 1, 2)))
 static int set_config(const char *fmt, ...)
 {
 	struct strbuf buf = STRBUF_INIT;

wt-status.c

@@ -126,6 +126,7 @@ void status_printf(struct wt_status *s, const char *color,
 	va_end(ap);
 }
 
+__attribute__((format (printf, 3, 4)))
 static void status_printf_more(struct wt_status *s, const char *color,
 			       const char *fmt, ...)
 {