GitLab Mattermost, an open source on-premises Slack alternative

This post announces the integration of GitLab Mattermost, an open-source, on-premises messaging app (similar to Slack), into GitLab Omnibus packages starting with version 7.14. This addresses the need for on-premises communication solutions for organizations that cannot use cloud-based services like Slack. The integration leverages GitLab's existing OAuth provider and Omnibus packaging for easy setup. The post also details the historical context of GitLab's internal communication tools, including the deprecated 'wall' feature, and the rationale for choosing Mattermost.