Add a note about —force-with-lease to contributing documentation.

CONTRIBUTING.md

@@ -36,6 +36,7 @@ Have questions about this document or anything not covered here? Come chat with
 - All code submissions are done through pull requests against the `devel` branch.
 - You must use `git commit --signoff` for any commit to be merged, and agree that usage of --signoff constitutes agreement with the terms of [DCO 1.1](./DCO_1_1.md).  
 - Take care to make sure no merge commits are in the submission, and use `git rebase` vs `git merge` for this reason.
+  - If collaborating with someone else on the same branch, consider using `--force-with-lease` instead of `--force`. This will prevent you from accidentally overwriting commits pushed by someone else. For more information, see https://git-scm.com/docs/git-push#git-push---force-with-leaseltrefnamegt
 - If submitting a large code change, it's a good idea to join the `#ansible-awx` channel on irc.freenode.net, and talk about what you would like to do or add first. This not only helps everyone know what's going on, it also helps save time and effort, if the community decides some changes are needed.
 - We ask all of our community members and contributors to adhere to the [Ansible code of conduct](http://docs.ansible.com/ansible/latest/community/code_of_conduct.html). If you have questions, or need assistance, please reach out to our community team at [[email protected]](mailto:[email protected])