FAQ: Describe how to integrate with Gerrit.

This question is mildly popular on Discord so it's finally time to have an answer.

We should do something better in the future but the current solution is good enough for today.

cc @thoughtpolice

docs/FAQ.md

@@ -157,12 +157,27 @@ Usually, the different commits associated with the conflicted branch should all
 appear in the log, but if they don't you can use `jj branch list`to show all the
 commits associated with it.
 
+### How do I integrate Jujutsu with Gerrit? 
+
+At the moment you'll need a script, which adds the required fields for Gerrit
+like the `Change-Id` footer. Then `jj` can invoke it via an `$EDITOR` override
+in an aliased command. Here's an [example][gerrit-integration] from an 
+contributor (look for the `jj signoff` alias).
+
+After you have attached the `Change-Id:` footer to the commit series, you'll 
+have to manually push `git push` your `HEAD` into the remote Gerrit branch
+`refs/for/$BRANCH`, where `$BRANCH` is the base branch you want your changes to
+go to.
+
+We hope to integrate with Gerrit natively in the future.
+
 [branches_conflicts]: branches.md#conflicts
 
 [change ID]: glossary.md#change-id
 [commit ID]: glossary.md#commit-id
 [config]: config.md
 
+[gerrit-integration]: https://gist.github.com/thoughtpolice/8f2fd36ae17cd11b8e7bd93a70e31ad6 
 [gitignore]: https://git-scm.com/docs/gitignore
 
 [glossary_divergent_change]: glossary.md#divergent-change