# Threads

The ability to contribute conversationally is offered throughout GitLab.

You can leave a comment in the following places:

- issues
- epics **(ULTIMATE)**
- merge requests
- snippets
- commits
- commit diffs

There are standard comments, and you also have the option to create a comment
in the form of a thread. A comment can also be [turned into a thread](#start-a-thread-by-replying-to-a-standard-comment)
when it receives a reply.

The comment area supports [Markdown] and [quick actions]. You can edit your own
comment at any time, and anyone with [Maintainer access level][permissions] or
higher can also edit a comment made by someone else.

You can also reply to a comment notification email to reply to the comment if
[Reply by email] is configured for your GitLab instance. Replying to a standard comment
creates another standard comment. Replying to a threaded comment creates a reply in the thread. Email replies support
 [Markdown] and [quick actions], just as if you replied from the web.

## Resolvable comments and threads

> **Notes:**
>
> - The main feature was [introduced][ce-5022] in GitLab 8.11.
> - Resolvable threads can be added only to merge request diffs.

Thread resolution helps keep track of progress during planning or code review.

Every standard comment or thread in merge requests, commits, commit diffs, and
snippets is initially displayed as unresolved. They can then be individually resolved by anyone
with at least Developer access to the project or by the author of the change being reviewed.

The need to resolve all standard comments or threads prevents you from forgetting
to address feedback and lets you hide threads that are no longer relevant.

!["A thread between two people on a piece of code"](img/thread_view.png)

### Commit threads in the context of a merge request

> [Introduced][ce-31847] in GitLab 10.3.

For reviewers with commit-based workflow, it may be useful to add threads to
specific commit diffs in the context of a merge request. These threads will
persist through a commit ID change when:

- force-pushing after a rebase
- amending a commit

To create a commit diff thread:

1. Navigate to the merge request **Commits** tab. A list of commits that
   constitute the merge request will be shown.

    ![Merge request commits tab](img/merge_request_commits_tab.png)

1. Navigate to a specific commit, click on the **Changes** tab (where you
   will only be presented diffs from the selected commit), and leave a comment.

    ![Commit diff discussion in merge request context](img/commit_comment_mr_context.png)

1. Any threads created this way will be shown in the merge request's
   **Discussions** tab and are resolvable.

    ![Merge request Discussions tab](img/commit_comment_mr_discussions_tab.png)

Threads created this way will only appear in the original merge request
and not when navigating to that commit under your project's
**Repository > Commits** page.

TIP: **Tip:**
When a link of a commit reference is found in a thread inside a merge
request, it will be automatically converted to a link in the context of the
current merge request.

### Jumping between unresolved threads

When a merge request has a large number of comments it can be difficult to track
what remains unresolved. You can jump between unresolved threads with the
Jump button next to the Reply field on a thread.

You can also jump to the first unresolved thread from the button next to the
resolved threads tracker.

!["8/9 threads resolved"](img/threads_resolved.png)

### Marking a comment or thread as resolved

You can mark a thread as resolved by clicking the **Resolve thread**
button at the bottom of the thread.

!["Resolve thread" button](img/resolve_thread_button.png)

Alternatively, you can mark each comment as resolved individually.

!["Resolve comment" button](img/resolve_comment_button.png)

### Move all unresolved threads in a merge request to an issue

> [Introduced][ce-8266] in GitLab 9.1

To continue all open threads from a merge request in a new issue, click the
**Resolve all threads in new issue** button.

![Open new issue for all unresolved threads](img/btn_new_issue_for_all_threads.png)

Alternatively, when your project only accepts merge requests [when all threads
are resolved](#only-allow-merge-requests-to-be-merged-if-all-threads-are-resolved),
there will be an **open an issue to resolve them later** link in the merge
request widget.

![Link in merge request widget](img/resolve_thread_open_issue.png)

This will prepare an issue with its content referring to the merge request and
the unresolved threads.

![Issue mentioning threads in a merge request](img/preview_issue_for_threads.png)

Hitting **Submit issue** will cause all threads to be marked as resolved and
add a note referring to the newly created issue.

![Mark threads as resolved notice](img/resolve_thread_issue_notice.png)

You can now proceed to merge the merge request from the UI.

### Moving a single thread to a new issue

> [Introduced][ce-8266] in GitLab 9.1

To create a new issue for a single thread, you can use the **Resolve this
thread in a new issue** button.

![Create issue for thread](img/new_issue_for_thread.png)

This will direct you to a new issue prefilled with the content of the
thread, similar to the issues created for delegating multiple
threads at once. Saving the issue will mark the thread as resolved and
add a note to the merge request thread referencing the new issue.

![New issue for a single thread](img/preview_issue_for_thread.png)

### Only allow merge requests to be merged if all threads are resolved

> [Introduced][ce-7125] in GitLab 8.14.

You can prevent merge requests from being merged until all threads are
resolved.

Navigate to your project's settings page, select the
**Only allow merge requests to be merged if all threads are resolved** check
box and hit **Save** for the changes to take effect.

![Only allow merge if all the threads are resolved settings](img/only_allow_merge_if_all_threads_are_resolved.png)

From now on, you will not be able to merge from the UI until all threads
are resolved.

![Only allow merge if all the threads are resolved message](img/resolve_thread_open_issue.png)

### Automatically resolve merge request diff threads when they become outdated

> [Introduced][ce-14053] in GitLab 10.0.

You can automatically resolve merge request diff threads on lines modified
with a new push.

Navigate to your project's settings page, select the **Automatically resolve
merge request diffs threads on lines changed with a push** check box and hit
**Save** for the changes to take effect.

![Automatically resolve merge request diff threads when they become outdated](img/automatically_resolve_outdated_discussions.png)

From now on, any threads on a diff will be resolved by default if a push
makes that diff section outdated. Threads on lines that don't change and
top-level resolvable threads are not automatically resolved.

## Commit threads

You can add comments and threads to a particular commit under your
project's **Repository > Commits**.

CAUTION: **Attention:**
Threads created this way will be lost if the commit ID changes after a
force push.

## Threaded discussions

> [Introduced][ce-7527] in GitLab 9.1.

While resolvable threads are only available to merge request diffs,
threads can also be added without a diff. You can start a specific
thread which will look like a thread, on issues, commits, snippets, and
merge requests.

To start a threaded discussion, click on the **Comment** button toggle dropdown,
select **Start thread** and click **Start thread** when you're ready to
post the comment.

![Comment type toggle](img/comment_type_toggle.gif)

This will post a comment with a single thread to allow you to discuss specific
comments in greater detail.

![Thread comment](img/discussion_comment.png)

## Image threads

> [Introduced][ce-14061] in GitLab 10.1.

Sometimes a thread is revolved around an image. With image threads,
you can easily target a specific coordinate of an image and start a thread
around it. Image threads are available in merge requests and commit detail views.

To start an image thread, hover your mouse over the image. Your mouse pointer
should convert into an icon, indicating that the image is available for commenting.
Simply click anywhere on the image to create a new thread.

![Start image thread](img/start_image_discussion.gif)

After you click on the image, a comment form will be displayed that would be the start
of your thread. Once you save your comment, you will see a new badge displayed on
top of your image. This badge represents your thread.

>**Note:**
This thread badge is typically associated with a number that is only used as a visual
reference for each thread. In the merge request thread tab,
this badge will be indicated with a comment icon since each thread will render a new
image section.

Image threads also work on diffs that replace an existing image. In this diff view
mode, you can toggle the different view modes and still see the thread point badges.

| 2-up | Swipe | Onion Skin |
| :-----------: | :----------: | :----------: |
| ![2-up view](img/two_up_view.png) | ![swipe view](img/swipe_view.png) | ![onion skin view](img/onion_skin_view.png) |

Image threads also work well with resolvable threads. Resolved threads
on diffs (not on the merge request discussion tab) will appear collapsed on page
load and will have a corresponding badge counter to match the counter on the image.

![Image resolved thread](img/image_resolved_discussion.png)

## Lock discussions

> [Introduced][ce-14531] in GitLab 10.1.

For large projects with many contributors, it may be useful to stop threads
in issues or merge requests in these scenarios:

- The project maintainer has already resolved the thread and it is not helpful
  for continued feedback.
- The project maintainer has already directed new conversation
  to newer issues or merge requests.
- The people participating in the thread are trolling, abusive, or otherwise
  being unproductive.

In these cases, a user with Developer permissions or higher in the project can lock (and unlock)
an issue or a merge request, using the "Lock" section in the sidebar. For issues,
a user with Reporter permissions can lock (and unlock).

| Unlock | Lock |
| :-----------: | :----------: |
| ![Turn off discussion lock](img/turn_off_lock.png) | ![Turn on discussion lock](img/turn_on_lock.png) |

System notes indicate locking and unlocking.

![Discussion lock system notes](img/discussion_lock_system_notes.png)

In a locked issue or merge request, only team members can add new comments and
edit existing comments. Non-team members are restricted from adding or editing comments.

| Team member | Non-team member |
| :-----------: | :----------: |
| ![Comment form member](img/lock_form_member.png) | ![Comment form non-member](img/lock_form_non_member.png) |

Additionally, locked issues and merge requests can not be reopened.

## Merge Request Reviews **(PREMIUM)**

> [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4213) in GitLab 11.4.

When looking at a Merge Request diff, you are able to start a review.
This allows you to create comments inside a Merge Request that are **only visible to you** until published,
in order to allow you to submit them all as a single action.

### Starting a review

In order to start a review, simply write a comment on a diff as normal under the **Changes** tab
in an MR and click on the **Start a review** button.

![Starting a review](img/mr_review_start.png)

Once a review is started, you will see any comments that are part of this review marked `Pending`.
All comments that are part of a review show two buttons:

- **Finish review**: Submits all comments that are part of the review, making them visible to other users.
- **Add comment now**: Submits the specific comment as a regular comment instead of as part of the review.

![A comment that is part of a review](img/pending_review_comment.png)

You can use [quick actions] inside review comments. The comment will show the actions that will be performed once published.

![A review comment with quick actions](img/review_comment_quickactions.png)

To add more comments to a review, start writing a comment as normal and click the **Add to review** button.

![Adding a second comment to a review](img/mr_review_second_comment.png)

This will add the comment to the review.

![Second review comment](img/mr_review_second_comment_added.png)

### Resolving/Unresolving threads

Review comments can also resolve/unresolve [resolvable threads](#resolvable-comments-and-threads).
When replying to a comment, you will see a checkbox that you can click in order to resolve or unresolve
the thread once published.

![Resolve checkbox](img/mr_review_resolve.png)

If a particular pending comment will resolve or unresolve the thread, this will be shown on the pending
comment itself.

![Resolve status](img/mr_review_resolve2.png)

![Unresolve status](img/mr_review_unresolve.png)

### Submitting a review

If you have any comments that have not been submitted, you will see a bar at the
bottom of the screen with two buttons:

- **Discard**: Discards all comments that have not been submitted.
- **Finish review**: Opens a list of comments ready to be submitted for review.
   Clicking **Submit review** will publish all comments. Any quick actions
   submitted are performed at this time.

Alternatively, every pending comment has a button to finish the entire review.

![Review submission](img/review_preview.png)

Submitting the review will send a single email to every notifiable user of the
merge request with all the comments associated to it.

Replying to this email will, consequentially, create a new comment on the associated merge request.

## Filtering notes

> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/26723) in GitLab 11.5.

For issues with many comments like activity notes and user comments, sometimes
finding useful information can be hard. There is a way to filter comments from single notes and threads for merge requests and issues.

From a merge request's **Discussion** tab, or from an epic/issue overview, find the filter's dropdown menu on the right side of the page, from which you can choose one of the following options:

- **Show all activity**: displays all user comments and system notes
  (issue updates, mentions from other issues, changes to the description, etc).
- **Show comments only**: only displays user comments in the list.
- **Show history only**: only displays activity notes.

![Notes filters dropdown options](img/index_notes_filters.png)

Once you select one of the filters in a given issue or MR, GitLab will save
your preference, so that it will persist when you visit the same page again
from any device you're logged into.

## Suggest Changes

> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/18008) in GitLab 11.6.

As a reviewer, you're able to suggest code changes with a simple
markdown syntax in Merge Request Diff threads. Then, the
Merge Request author (or other users with appropriate
[permission](../permissions.md)) is able to apply these
suggestions with a click, which will generate a commit in
the Merge Request authored by the user that applied them.

1. Choose a line of code to be changed, add a new comment, then click
   on the **Insert suggestion** icon in the toolbar:

    ![Add a new comment](img/insert_suggestion.png)

1. In the comment, add your suggestion to the pre-populated code block:

    ![Add a suggestion into a code block tagged properly](img/make_suggestion.png)

1. Click **Comment**.

    The suggestions in the comment can be applied by the merge request author
    directly from the merge request:

    ![Apply suggestions](img/suggestion.png)

Once the author applies a suggestion, it will be marked with the **Applied** label,
the thread will be automatically resolved, and GitLab will create a new commit
with the message `Apply suggestion to <file-name>` and push the suggested change
directly into the codebase in the merge request's branch.
[Developer permission](../permissions.md) is required to do so.

> **Note:**
Custom commit messages will be introduced by
[#54404](https://gitlab.com/gitlab-org/gitlab-ce/issues/54404).

### Multi-line suggestions

> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/53310) in GitLab 11.10.

Reviewers can also suggest changes to multiple lines with a single suggestion
within Merge Request diff threads by adjusting the range offsets. The
offsets are relative to the position of the diff thread, and specify the
range to be replaced by the suggestion when it is applied.

![Multi-line suggestion syntax](img/multi-line-suggestion-syntax.png)

In the example above, the suggestion covers three lines above and four lines
below the commented line. When applied, it would replace from 3 lines _above_
to 4 lines _below_ the commented line, with the suggested change.

![Multi-line suggestion preview](img/multi-line-suggestion-preview.png)

NOTE: **Note:**
Suggestions covering multiple lines are limited to 100 lines _above_ and 100
lines _below_ the commented diff line, allowing up to 200 changed lines per
suggestion.

## Start a thread by replying to a standard comment

> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/30299) in GitLab 11.9

To reply to a standard (non-thread) comment, you can use the **Reply to comment** button.

![Reply to comment button](img/reply_to_comment_button.png)

The **Reply to comment** button is only displayed if you have permissions to reply to an existing thread, or start a thread from a standard comment.

Clicking on the **Reply to comment** button will bring the reply area into focus and you can type your reply.

![Reply to comment feature](img/reply_to_comment.gif)

Replying to a non-thread comment will convert the non-thread comment to a
thread once the reply is submitted. This conversion is considered an edit
to the original comment, so a note about when it was last edited will appear underneath it.

This feature only exists for Issues, Merge requests, and Epics. Commits, Snippets and Merge request diff threads are 
not supported yet.

[ce-5022]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5022
[ce-7125]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7125
[ce-7527]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7527
[ce-7180]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7180
[ce-8266]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8266
[ce-14053]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14053
[ce-14061]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14061
[ce-14531]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14531
[ce-31847]: https://gitlab.com/gitlab-org/gitlab-ce/issues/31847
[resolve-discussion-button]: img/resolve_discussion_button.png
[resolve-comment-button]: img/resolve_comment_button.png
[discussion-view]: img/discussion_view.png
[discussions-resolved]: img/discussions_resolved.png
[markdown]: ../markdown.md
[quick actions]: ../project/quick_actions.md
[permissions]: ../permissions.md
[Reply by email]: ../../administration/reply_by_email.md
