extern void trace_argv_printf(const char **argv, const char *format, ...);
extern void trace_repo_setup(const char *prefix);
extern int trace_want(const char *key);
+__attribute__((format (printf, 2, 3)))
+extern void trace_printf_key(const char *key, const char *fmt, ...);
extern void trace_strbuf(const char *key, const struct strbuf *buf);
void packet_trace_identity(const char *prog);