Select additional folders that contain the source code files of the job. Since the plugin also reads the affected source code files it needs to copy these files from the agent to the controller. If these files are not part of the workspace (or checked out into a sub folder of the workspace) they are not automatically found. So you can add one or more source code directories where the plugin tries to find these files. You can add relative paths in the workspace root, absolute paths, or expressions using the glob or regexp syntaxes that are supported by the Java FileSystem#getPathMatcher implementation. Note, that due to security restrictions additional paths outside the workspace need to be registered in Jenkins system configuration before they can be used here.

Examples for the syntax and pattern property:
submodule/src/main/java
Relative path submodule/src/main/java in the Jenkins workspace.
glob:**/src/main/java
A glob that expands to all folders in the Jenkins workspace that contain the sub-path src/main/java.
regex:sources.*/src/main/java
A regular expression that matches all folders in the Jenkins workspace that start with sources and end with the text src/main/java.
C:\work\sources
Absolute path on the agent that builds the sources. This folder must also be approved by a Jenkins administrator in Jenkins global configuration.