Merge branch 'jk/snprintf-truncation'

Avoid unchecked snprintf() to make future code auditing easier.

* jk/snprintf-truncation:
  fmt_with_err: add a comment that truncation is OK
  shorten_unambiguous_ref: use xsnprintf
  fsmonitor: use internal argv_array of struct child_process
  log_write_email_headers: use strbufs
  http: use strbufs instead of fixed buffers

usage.c

@@ -148,6 +148,7 @@ static const char *fmt_with_err(char *buf, int n, const char *fmt)
 		}
 	}
 	str_error[j] = 0;
+	/* Truncation is acceptable here */
 	snprintf(buf, n, "%s: %s", fmt, str_error);
 	return buf;
 }