rn-49: add news about git-graph

Author: chriscool

rev_news/drafts/edition-49.md

@@ -151,6 +151,11 @@ __Git tools and sites__
 *[radicle](http://radicle.xyz/) is a peer-to-peer stack for code
  collaboration based on Git and [IPFS](https://ipfs.io/).
 
+*[Git-graph](https://github.com/hoduche/git-graph) by
+[Henri-Olivier Duché](https://github.com/hoduche)
+ can help you "Learn Git fast and well - by visualizing the inner graph of your Git
+ repositories".
+
 ## Credits
 
 This edition of Git Rev News was curated by