StashBuildTrigger: Make field defaults match config.jelly

That makes the Pipeline Snippet Generator skip arguments from the trigger
call if those arguments have default values.

Keep default values for the skip phrase and the build phrase in the
descriptor, so they can be used both in config.jelly and in the code.

Author: proski

src/main/java/stashpullrequestbuilder/stashpullrequestbuilder/StashBuildTrigger.java

@@ -44,17 +44,17 @@ public class StashBuildTrigger extends Trigger<Job<?, ?>> {
 
   // Optional settings
   private boolean ignoreSsl;
-  private String targetBranchesToBuild;
+  private String targetBranchesToBuild = "";
   private boolean checkDestinationCommit;
   private boolean checkNotConflicted;
   private boolean checkMergeable;
-  private boolean checkProbeMergeStatus;
+  private boolean checkProbeMergeStatus = true;
   private boolean mergeOnSuccess;
   private boolean deletePreviousBuildFinishComments;
   private boolean cancelOutdatedJobsEnabled;
-  private String ciSkipPhrases;
+  private String ciSkipPhrases = DescriptorImpl.DEFAULT_CI_SKIP_PHRASES;
   private boolean onlyBuildOnComment;
-  private String ciBuildPhrases;
+  private String ciBuildPhrases = DescriptorImpl.DEFAULT_CI_BUILD_PHRASES;
 
   private transient StashPullRequestsBuilder stashPullRequestsBuilder;
 
@@ -217,7 +217,7 @@ public void setOnlyBuildOnComment(boolean onlyBuildOnComment) {
   }
 
   public String getCiBuildPhrases() {
-    return ciBuildPhrases == null ? "test this please" : ciBuildPhrases;
+    return ciBuildPhrases;
   }
 
   @DataBoundSetter
@@ -264,6 +264,9 @@ public void stop() {
   }
 
   public static final class DescriptorImpl extends TriggerDescriptor {
+    public static final String DEFAULT_CI_SKIP_PHRASES = "NO TEST";
+    public static final String DEFAULT_CI_BUILD_PHRASES = "test this please";
+
     public DescriptorImpl() {
       load();
     }

src/main/resources/stashpullrequestbuilder/stashpullrequestbuilder/StashBuildTrigger/config.jelly

@@ -44,13 +44,13 @@
       <f:checkbox default="false"/>
     </f:entry>
     <f:entry title="Phrase to disable builds" field="ciSkipPhrases">
-      <f:textbox default="NO TEST" />
+      <f:textbox default="${descriptor.DEFAULT_CI_SKIP_PHRASES}"/>
     </f:entry>
     <f:entry title="Only build if asked with the build phrase" field="onlyBuildOnComment">
       <f:checkbox default="false"/>
     </f:entry>
     <f:entry title="Phrase to request a (re-)build" field="ciBuildPhrases">
-      <f:textbox default="test this please"/>
+      <f:textbox default="${descriptor.DEFAULT_CI_BUILD_PHRASES}"/>
     </f:entry>
   </f:advanced>
 </j:jelly>