Remove StashBuilds#getCause(), call build.getCause() directly

The "build" argument in onStarted() and onCompleted() is not of a raw
type anymore, which enables type-safe behavior without casts.

build.getCause() returns a value of the type provided in its argument. If
cause is null or there is no cause of the given type, build.getCause()
returns null.

That is the desired behavior. No extra wrapper is required.

Author: proski

src/main/java/stashpullrequestbuilder/stashpullrequestbuilder/StashBuilds.java

@@ -2,7 +2,6 @@
 
 import hudson.Util;
 import hudson.model.AbstractBuild;
-import hudson.model.Cause;
 import hudson.model.Result;
 import hudson.model.TaskListener;
 import java.io.IOException;
@@ -23,16 +22,8 @@ public StashBuilds(StashBuildTrigger trigger, StashRepository repository) {
     this.repository = repository;
   }
 
-  public StashCause getCause(AbstractBuild build) {
-    Cause cause = build.getCause(StashCause.class);
-    if (cause == null || !(cause instanceof StashCause)) {
-      return null;
-    }
-    return (StashCause) cause;
-  }
-
   public void onStarted(AbstractBuild<?, ?> build) {
-    StashCause cause = this.getCause(build);
+    StashCause cause = build.getCause(StashCause.class);
     if (cause == null) {
       return;
     }
@@ -44,7 +35,7 @@ public void onStarted(AbstractBuild<?, ?> build) {
   }
 
   public void onCompleted(AbstractBuild<?, ?> build, TaskListener listener) {
-    StashCause cause = this.getCause(build);
+    StashCause cause = build.getCause(StashCause.class);
     if (cause == null) {
       return;
     }