* Create a detached signature for the contents of "buffer" and append
* it after "signature"; "buffer" and "signature" can be the same
* strbuf instance, which would cause the detached signature appended
- * at the end.
+ * at the end. Returns 0 on success, non-zero on failure.
*/
int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
const char *signing_key);