Merge branch 'docs-article-undo-things-in-git' into 'master'

Docs: article - "Numerous undo possibilities in Git"

Closes gitlab-com/community-writers#40

See merge request !13513

doc/topics/git/index.md

@@ -22,6 +22,7 @@ We've gathered some resources to help you to get the best from Git with GitLab.
   - [Cherry-picking a commit](../../user/project/merge_requests/cherry_pick_changes.md#cherry-picking-a-commit)
   - [Squashing commits](../../workflow/gitlab_flow.md#squashing-commits-with-rebase)
 - **Articles:**
+  - [Numerous _undo_ possibilities in Git](../../articles/numerous_undo_possibilities_in_git/index.md)
   - [How to install Git](../../articles/how_to_install_git/index.md)
   - [Git Tips & Tricks](https://about.gitlab.com/2016/12/08/git-tips-and-tricks/)
   - [Eight Tips to help you work better with Git](https://about.gitlab.com/2015/02/19/8-tips-to-help-you-work-better-with-git/)