Added Rake task for tracking deployments

This simply inserts the current GitLab version in the "deployments"
measurement.

Fixes gitlab-com/infrastructure#98

CHANGELOG

@@ -31,6 +31,7 @@ v 8.10.0 (unreleased)
   - Support U2F devices in Firefox. !5177
   - Fix issue, preventing users w/o push access to sort tags !5105 (redetection)
   - Add Spring EmojiOne updates.
+  - Added Rake task for tracking deployments !5320
   - Fix fetching LFS objects for private CI projects
   - Add syntax for multiline blockquote using `>>>` fence !3954
   - Fix viewing notification settings when a project is pending deletion

doc/raketasks/maintenance.md

@@ -167,3 +167,22 @@ of those assets. Unless you are modifying the JavaScript / CSS code on your
 production machine after installing the package, there should be no reason to redo
 rake assets:precompile on the production machine. If you suspect that assets
 have been corrupted, you should reinstall the omnibus package.
+
+## Tracking Deployments
+
+GitLab provides a Rake task that lets you track deployments in GitLab
+Performance Monitoring. This Rake task simply stores the current GitLab version
+in the GitLab Performance Monitoring database.
+
+For Omnibus-packages:
+
+```
+sudo gitlab-rake gitlab:track_deployment
+```
+
+For installations from source:
+
+```
+cd /home/git/gitlab
+sudo -u git -H bundle exec rake gitlab:track_deployment RAILS_ENV=production
+```

lib/tasks/gitlab/track_deployment.rake

+namespace :gitlab do
+  desc 'GitLab | Tracks a deployment in GitLab Performance Monitoring'
+  task track_deployment: :environment do
+    metric = Gitlab::Metrics::Metric.
+      new('deployments', version: Gitlab::VERSION)
+
+    Gitlab::Metrics.submit_metrics([metric.to_hash])
+  end
+end