add missing "format" function attributes

For most of our functions that take printf-like formats, we
use gcc's __attribute__((format)) to get compiler warnings
when the functions are misused. Let's give a few more
functions the same protection.

In most cases, the annotations do not uncover any actual
bugs; the only code change needed is that we passed a size_t
to transfer_debug, which expected an int. Since we expect
the passed-in value to be a relatively small buffer size
(and cast a similar value to int directly below), we can
just cast away the problem.

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

advice.h

@@ -19,6 +19,7 @@ extern int advice_detached_head;
 extern int advice_set_upstream_failure;
 
 int git_default_advice_config(const char *var, const char *value);
+__attribute__((format (printf, 1, 2)))
 void advise(const char *advice, ...);
 int error_resolve_conflict(const char *me);
 extern void NORETURN die_resolve_conflict(const char *me);

trace.c

@@ -75,6 +75,7 @@ static void trace_vprintf(const char *key, const char *fmt, va_list ap)
 	strbuf_release(&buf);
 }
 
+__attribute__((format (printf, 2, 3)))
 static void trace_printf_key(const char *key, const char *fmt, ...)
 {
 	va_list ap;

transport-helper.c

@@ -955,6 +955,7 @@ int transport_helper_init(struct transport *transport, const char *name)
 #define PBUFFERSIZE 8192
 
 /* Print bidirectional transfer loop debug message. */
+__attribute__((format (printf, 1, 2)))
 static void transfer_debug(const char *fmt, ...)
 {
 	va_list args;
@@ -1040,7 +1041,7 @@ static int udt_do_read(struct unidirectional_transfer *t)
 		return -1;
 	} else if (bytes == 0) {
 		transfer_debug("%s EOF (with %i bytes in buffer)",
-			t->src_name, t->bufuse);
+			t->src_name, (int)t->bufuse);
 		t->state = SSTATE_FLUSHING;
 	} else if (bytes > 0) {
 		t->bufuse += bytes;

utf8.h

@@ -10,6 +10,7 @@ int utf8_strwidth(const char *string);
 int is_utf8(const char *text);
 int is_encoding_utf8(const char *name);
 int same_encoding(const char *, const char *);
+__attribute__((format (printf, 2, 3)))
 int utf8_fprintf(FILE *, const char *, ...);
 
 void strbuf_add_wrapped_text(struct strbuf *buf,