This is GHC's GitLab instance. GitLab has replaced Trac and Phabricator as the center of GHC's development community.
You may wish to see the table of contents to get a sense for what is available in this Wiki.
If you had a Trac account then you likely already have a GitLab account as a result of the Trac import. This account will have a username of the form
trac-$TRAC_USERNAME. You can reset your password with the Forgot your password? dialogue. Once you have gained access to this account you may change your username to remove the
As a last resort, please contact @bgamari with your email address.
Submitting a patch for incorporation into the tree is done by creating a merge request. The merge request serves as a place to conduct code review, collect continuous integration results, and eventually merge your patch.
Opening a merge request
To open a merge request:
- Push your branch. You may push either to your fork or the primary
- Starting from the GHC GitLab project click on the Merge Requests link in the left navigational bar.
- Click on the green New Merge Request button on the top right corner of the Merge Requests page
- In the left drop-down of the Source branch pane select the project to which you pushed your branch.
- In the right drop-down of the Source branch pane select the name of your branch.
- Click on the green Compare branches and continue button.
- Give your merge request a title
- Write a description of your change. This should be ideally at very least a few sentences to help reviewers understand what you have done.
- Click on the green Submit merge request button.
Working with your merge request
Your merge request shows you several panes information:
Top-most is the request's title and description. These can be edited by pressing the yellow
Edit button on the top-right corner of the page.
The next pane summarises your merge request, showing the the source and target branches.
The next pane shows the status of the merge request's continuous integration builds. If the build has failed you can click on the red X icon to see the build log.
At the bottom of the page is the code review interface, consisting of several tabs:
The Discussion tab shows a summary of the comments left on the change. This includes comments left in-line in the code, as well as those independent of the code.
The Commits tab lists the commits being proposed for merge. These may be clicked upon to restrict the diff to only changes made by that commit.
The Pipelines tab provides a more detailed overview on the state of the various continuous integration jobs associated with the merge request.
Finally, the Changes tab shows the patch itself. This view may be restricted to changes made by a single commit by selecting the commit in the Commits tab. Moreover, one may view previous iterations of the merge request using the two drop-down menus at the top of the tab. To leave an inline comment click on a line in the patch.
Merging your merge request
Currently we merge MRs with the aid of @marge-bot. After your MR has been reviewed and approved by a GHC developer you can flag it for merge by assigning it to @marge-bot using the "Assignee" field in the right sidebar:
As long as your MR satisfies the following, marge will batch your MR with other MRs and attempt to merge into master:
- Assigned to Marge
- Approved by a GHC developer
- Passing CI
- Has no merge conflicts with master (see rebasing below)
Each batch is an MR and must pass CI, so you can expect Marge to merge 2 or 3 batches per day. She will usually comment on your MR to inform you of progress, but you can also view the status of Marge's batches/MRs on GitLab.
You generally do NOT need to rebase your MRs unless there are merge conflicts with master. Marge will automatically rebase ontop of master when batching MRs.
Note GitLab usually complains that "Fast-forward merge is not possible" on your MR. If you see a green check and green "Rebase" button then there are no merge conflicts and NO action is necessary. If instead you see an exclamation mark and disabled "Merge" button, you must rebase manually and fix any merge conflicts.
Migration from Trac
Most of the tickets here were carried over from GHC's previous Trac installation. See the wiki for details about this migration.