Add info about when Revert might be disabled

Author: ghogen

docs/version-control/git-manage-repository.md

@@ -142,6 +142,8 @@ Select the new commit to confirm that it undoes the changes of the reverted comm
 
 :::image type="content" source="media/vs-2022/git-repository-revert-confirmation.png" alt-text="Screenshot of confirming a revert operation." lightbox="media/vs-2022/git-repository-revert-confirmation.png":::
 
+The **Revert** menu item might be grayed out (disabled) in certain circumstances, such as for merge commits or when a git operation is running.
+
 To learn more about reverting changes, see the [Git webpage for the revert command](https://git-scm.com/docs/git-revert).
 
 ## Reset a branch to a previous state