There are a couple of slash-commands available on GitHub which are implemented via Mattermod. They only work on PRs.
The commands are:
/cherry-pick $BRANCH_NAME, e.g.
/cherry-pick release-5.10: Opens a PR to cherry pick a change into the branch
$BRANCH_NAME. This command only works for members of the Mattermost organization.
/check-cla: Checks if the PR contributor has signed the CLA.
/autoassign: Automatically assigns reviewers to a PR.
/update-branch: Updates the pull request branch with the latest upstream changes by merging HEAD from the base branch into the pull request branch. This command only works for members of the Mattermost organization.