added signing git commings smime

mission/publications.md

@@ -39,6 +39,7 @@ excerpt:
   * [Collaborative Notetaking]({% post_url 2020/06/2020-06-26-guidelines-for-collaborative-notetaking %})
   * [Video Conferencing]({% post_url 2020/05/2020-05-15-guidelines-for-video-conferencing %})
   * [Chatting]({% post_url 2020/05/2020-05-15-guidelines-for-chatting %})
+* [**S/MIME Signing Git Commits**](https://software.hifis.net/tutorial/2020/04/15/smime-signing-git-commits), Blog post, April 2020.
 * [**The HIFIS Cloud Competence Cluster**](https://indico.cern.ch/event/854707/contributions/3680436/). In: [CS3 2020 Workshop on Cloud Services for Synchronisation and Sharing](https://cs3.deic.dk/), January 2020.
 
 ##### 2019