releasing package dulwich version 0.18.4-1

debian/changelog

@@ -1,4 +1,4 @@
-dulwich (0.18.4-1) UNRELEASED; urgency=medium
+dulwich (0.18.4-1) unstable; urgency=medium
 
   * New upstream release.
   * Bump standards version to 4.1.1 (no changes).