How do I change thee Custom checkout directory to have prefix?

My project requires to be within a folder structure, where every directory starts with letter (it generate c++ symbols from path), but checkout directory is by default

<Agent Work Directory>/<VCS settings hash code>

and the hash does't begin with letter. I've found where to change it (Checkout Options-> show advanced). I would like to preserve the feature, when directory is preserved, until git settings change, but need to add prefix, so I would like to have something like

<Agent Work Directory>/prefix_<VCS settings hash code>

but how do I do it? I've not found TC variable for <VCS settings hash code>

%teamcity.agent.work.dir%/resist%????%