Allows build Steps to be performed before the SCM performs any modification to the workspace,
Warnings:
The SCM may modify or remove any files that are in the workspace, before the main build steps.
Enviroment variables may not exist at this point, if they are created by other plugins, check using a shell script and the env (unix) or equivalent for your executor system.
IMPORTANT: Failed build steps will not cause the job to fail at this point, and all build steps will be called regardless of the result.