Updating GitLab Mattermost to 4.2 for GitLab 10.0 release

Merged username-removed-570793 requested to merge jasonblais/omnibus-gitlab:patch-10 into master

Mattermost 4.2 has been tested with GitLab SSO with official release on September 16 from https://about.mattermost.com/download/. Mattermost team is ready to test GitLab 10.0 omnibus RC for both upgrade and new install.

Key updates this release:

  • Interactive message buttons (Beta)
  • Support for Slack-compatible delayed slash commands through the response_url parameter

Full release notes can be found here. Changes to Mattermost config.json are documented in release notes.

There are security updates in Mattermost 4.2 affecting Team Edition so upgrading is recommended. Backports to 4.1 and 4.0 containing the security fixes will be submitted soon.