On invoking Project#build! in-queue builds are pruned

app/models/project.rb

@@ -23,12 +23,12 @@ def recent_build
 
   def build!
     new_total_builds = self.total_builds + 1
-    build = nil
     ActiveRecord::Base.transaction do
       build = self.builds.create!({:scheduled_at => Time.now, :build_no => new_total_builds})
       self.update_attributes!(:total_builds => new_total_builds)
+      remove_project_jobs_in_queue()
+      Delayed::Job.enqueue(build)
     end
-    Delayed::Job.enqueue(build)
   end
 
   def hooks
@@ -119,4 +119,16 @@ def update_hooks
       Hook.create!(:project => self, :hook_name => name)
     end
   end
+
+  def remove_project_jobs_in_queue
+    jobs_to_destroy = []
+    Delayed::Job.all.each do |job|
+      build = job.payload_object
+      next unless build.is_a?(Build)
+      if build.status = Build::STATUS_IN_QUEUE && build.project == self
+        jobs_to_destroy << job
+      end
+    end
+    jobs_to_destroy.each { |job| job.destroy }
+  end
 end

test/unit/project_test.rb

@@ -203,6 +203,13 @@ def teardown
     assert ! commands.include?('#not5')
   end
 
+  test "invoking #build! cancels previously queued build" do
+    project = project_with_steps({:vcs_source => "test/files/repo"}, "true", "true\nfalse")
+    assert_difference("Delayed::Job.count", +1) do
+      3.times { project.build! }
+    end
+  end
+
   private
   def create_project_builds(project, *statuses)
     statuses.reverse.each do |status|