git-whatchanged: Add usage string

diff --git a/csum-file.h b/csum-file.h
index 776cfb152af2b6c4fb6c190d875b4fb2f9162c9a..3ad1a992a758fc9339baa2cecc17ac14af359f1b 100644 (file)
--- a/csum-file.h
+++ b/csum-file.h
@@ -11,7 +11,7 @@ struct sha1file {
 };
 
 extern struct sha1file *sha1fd(int fd, const char *name);
-extern struct sha1file *sha1create(const char *fmt, ...);
+extern struct sha1file *sha1create(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
 extern int sha1close(struct sha1file *, unsigned char *, int);
 extern int sha1write(struct sha1file *, void *, unsigned int);
 extern int sha1write_compressed(struct sha1file *, void *, unsigned int);