In the past TeamCity allowed us to spoof the branch we ran a build configuration on. We were going to utilise this with each differential revision having its own TeamCity branch. However in a recent change (post 2018.2.2) branches specified in builds must have a corresponding VCS branch otherwise the build is marked as failed. We therefore don't need a branch name within the teamcity plugin.
We are still passing through the REVISION_BUILD to allow us to display the snapshot within TeamCity.
We were previously setting the phabricator variabels we needs within builds to be environment variables however there are issues arount pulling out ENVS when on the agent within `buildStarted` step. To resolve the lack of environment variable access we are going to use sharedParameters which also doesn't work with variables prefixed with `env.` hence the rename.
To make sure there are no naming conflicts with teamcity environment variable we are renaming the vars injected to the build via the harbormaster trigger.
