When checking out (looking in job's console output), local files are getting not directly to the JobName@script folder but also add a subfolder with name like ecb7a9317b1ad672698830264d9e0ce2b9b6f330c043bb85f48623f3cdcab65e

Checking out git git@...repo.git into /Users/user/.jenkins/workspace/JobName@script/ecb7a9317b1ad672698830264d9e0ce2b9b6f330c043bb85f48623f3cdcab65e/jenkins/A.groovy

Loading the main groovy file here:

Project to build located directly in Job Name folder, without subfolders. But scripts put in subfolder.

Now, when in A.groovy I am trying to import B.groovy 

load("jenkins/B.groovy")
or
load(env.WORKSPACE + "@script/jenkins/B.groovy") 

I am getting an error 

java.nio.file.NoSuchFileException:
/Users/user/.jenkins/workspace/JobName@script/jenkins/B.groovy

And don't see any way to get that subfolder name from environment or other way. Thus just can't load an external file.