The Git plugin should now be able to expand environment variables and use them for the checkouts, such as the branch specifier. This works completely fine when specifying a branch name. It also worked fine when entering a commit ID manually. 

However, it fails when I combine the two and add the commit ID as a parameter, which is then used for the branch (see attached screenshot). The plugin will treat it as a regular branch name and fails to do the checkout.

stderr: fatal: couldn't find remote ref refs/heads/62f7ad718b0d427b7fd0cb0fe15a615308c41d92
My workaround for now is to use the branch name instead of the commit hash.