When executed by a branch pipeline in EE, we add an additional tag
destination using the commit SHA truncated to 11 characters, which is
what will be used by the Omnibus auto-deploy tag.

This allows auto-deploy package builds to fetch the asset image directly
for a specific commit without rebuilding assets itself, and without
performing an API call to expand the full SHA.

This will potentially remove about 8 minutes from auto-deploy package
builds.