Gitlab CI variables: commit description

We are using Gitlab CI to make our build and publish them trough Octopus. So far everything is working fine, but we lose all information regarding what triggered this build.
More specifically, when a feature branch is merged into master, it would be great if we could have access to the Commit description as this states which branch was merged into the master.

I did not find this in the list of available variables so I was wondering if I missed something or if this is at all possible to do?
We are using PowerShell for our builds by the way



We send a issu about this !