eslint taking 30+ minutes in Commit Queue

We are seeing a lot of instances in the commit queue of eslint taking 30+ minutes. After some discussion, it seems like changes might not be using the correct git diff and causing the task to lint the entire code base.

Here is a sample task that hit 36 minutes.

From Jonathan Brill:

I think it should work if we diff the upstream master with the working tree, something like git diff master@{upstream}, substituting the branch name of the project for master (I think there's a "branch_name" expansion).

This should work whether or not the patch is a commit queue patch.