Add support for Nth build failure for Email Extension plugin

job-dsl-core/src/main/groovy/javaposse/jobdsl/dsl/helpers/publisher/ExtendedEmailTriggerContext.groovy

@@ -17,6 +17,7 @@ class ExtendedEmailTriggerContext implements Context {
     boolean attachBuildLog
     boolean compressBuildLog
     final List<String> replyToList = []
+    int failureCount = -1
 
     /**
      * Specifies the email recipients.
@@ -88,4 +89,11 @@ class ExtendedEmailTriggerContext implements Context {
     void replyToList(String... replyToList) {
         this.replyToList.addAll(replyToList)
     }
+
+    /**
+     * Specifies the failure count to be applied to the xNthFailure use case.
+     */
+    void failureCount(int failureCount) {
+        this.failureCount = failureCount
+    }
 }

job-dsl-core/src/main/groovy/javaposse/jobdsl/dsl/helpers/publisher/ExtendedEmailTriggersContext.groovy

@@ -42,6 +42,13 @@ class ExtendedEmailTriggersContext implements Context {
         addTrigger('SecondFailure', closure)
     }
 
+    /**
+     * Triggers an email when the build fails n times in a row after a successful build
+     */
+    void xNthFailure(@DslContext(ExtendedEmailTriggerContext) Closure closure = null) {
+        addTrigger('XNthFailure', closure)
+    }
+
     /**
      * Triggers an email any time the build fails.
      */
@@ -131,6 +138,9 @@ class ExtendedEmailTriggersContext implements Context {
         ContextHelper.executeInContext(closure, context)
 
         configuredTriggers << new NodeBuilder()."hudson.plugins.emailext.plugins.trigger.${name}Trigger" {
+            if (context.failureCount != -1) {
+                requiredFailureCount(context.failureCount)
+            }
             email {
                 recipientList(context.recipientList.join(', '))
                 subject(context.subject ?: '')

job-dsl-core/src/test/groovy/javaposse/jobdsl/dsl/helpers/publisher/PublisherContextSpec.groovy

@@ -231,6 +231,7 @@ class PublisherContextSpec extends Specification {
         'firstUnstable'  || 'FirstUnstableTrigger'
         'stillUnstable'  || 'StillUnstableTrigger'
         'fixedUnhealthy' || 'FixedUnhealthyTrigger'
+        'xNthFailure'    || 'XNthFailureTrigger'
     }
 
     def 'call standard mailer method'() {