In MatrixConfiguration get ScmCheckoutStrategy from parent

changelog.html

@@ -63,6 +63,9 @@ Upcoming changes</a>
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-14538">issue 14538</a>)
   <li class=bug>
     Custom workspace in matrix projects should be able to use axis as variables.
+  <li class=bug>
+    New <tt>SCMCheckoutStrategy</tt> extension wasn't workin for matrix projects.
+    (<a href="https://github.com/jenkinsci/jenkins/pull/519">pull 519</a>)
   <li class=bug>
     Fixed a problem in the concurrent matrix build.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-13972">issue 13972</a>)

core/src/main/java/hudson/matrix/MatrixConfiguration.java

@@ -46,6 +46,7 @@ import hudson.model.SCMedItem;
 import hudson.model.Queue.NonBlockingTask;
 import hudson.model.Cause.LegacyCodeCause;
 import hudson.scm.SCM;
+import jenkins.scm.SCMCheckoutStrategy;
 import hudson.tasks.BuildWrapper;
 import hudson.tasks.Builder;
 import hudson.tasks.LogRotator;
@@ -185,6 +186,14 @@ public class MatrixConfiguration extends Project<MatrixConfiguration,MatrixRun>
         return getParent().getScmCheckoutRetryCount();
     }
 
+    /**
+     * Inherit the value from the parent.
+     */
+    @Override
+    public SCMCheckoutStrategy getScmCheckoutStrategy() {
+        return getParent().getScmCheckoutStrategy();
+    }
+ 
     @Override
     public boolean isConfigurable() {
         return false;