Introduced in GitLab 8.11.
Discussion resolution helps keep track of progress during code review. Resolving comments prevents you from forgetting to address feedback and lets you hide discussions that are no longer relevant.
Comments and discussions can be resolved by anyone with at least Developer access to the project, as well as by the author of the merge request.
You can mark a discussion as resolved by clicking the "Resolve discussion" button at the bottom of the discussion.
Alternatively, you can mark each comment as resolved individually.
When a merge request has a large number of comments it can be difficult to track what remains unresolved. You can jump between unresolved discussions with the Jump button next to the Reply field on a discussion.
You can also jump to the first unresolved discussion from the button next to the resolved discussions tracker.
Introduced in GitLab 8.14.
You can prevent merge requests from being merged until all discussions are resolved.
Navigate to your project's settings page, select the Only allow merge requests to be merged if all discussions are resolved check box and hit Save for the changes to take effect.
From now on, you will not be able to merge from the UI until all discussions are resolved.
Introduced in GitLab 8.15.
To delegate unresolved discussions to a new issue you can click the link open an issue to resolve them later.
This will prepare an issue with content referring to the merge request and discussions.
Hitting Submit issue will cause all discussions to be marked as resolved and add a note referring to the newly created issue.
You can now proceed to merge the merge request from the UI.