releasing package dulwich version 0.12.0-1

debian/changelog

@@ -1,4 +1,4 @@
-dulwich (0.12.0-1) UNRELEASED; urgency=medium
+dulwich (0.12.0-1) unstable; urgency=medium
 
   * New upstream release.
   * Drop patch 02_cgit_c: applied upstream.