'git mv' rst resources to md

This is mainly intended to keep the git history as neat as possible.
No actual conversion yet, so now both the rst and the paradox docs
are broken, which will be fixed in the next commits.

akka-docs/src/main/paradox/scala/code/docs/stream/GraphCyclesSpec.scala

@@ -0,0 +1,110 @@
+package docs.stream
+
+import akka.stream.{ ClosedShape, OverflowStrategy, ActorMaterializer }
+import akka.stream.scaladsl._
+import akka.testkit.AkkaSpec
+
+class GraphCyclesSpec extends AkkaSpec {
+
+  implicit val materializer = ActorMaterializer()
+
+  "Cycle demonstration" must {
+    val source = Source.fromIterator(() => Iterator.from(0))
+
+    "include a deadlocked cycle" in {
+
+      // format: OFF
+      //#deadlocked
+      // WARNING! The graph below deadlocks!
+      RunnableGraph.fromGraph(GraphDSL.create() { implicit b =>
+        import GraphDSL.Implicits._
+
+        val merge = b.add(Merge[Int](2))
+        val bcast = b.add(Broadcast[Int](2))
+
+        source ~> merge ~> Flow[Int].map { s => println(s); s } ~> bcast ~> Sink.ignore
+                  merge                    <~                      bcast
+        ClosedShape
+      })
+      //#deadlocked
+      // format: ON
+    }
+
+    "include an unfair cycle" in {
+      // format: OFF
+      //#unfair
+      // WARNING! The graph below stops consuming from "source" after a few steps
+      RunnableGraph.fromGraph(GraphDSL.create() { implicit b =>
+        import GraphDSL.Implicits._
+
+        val merge = b.add(MergePreferred[Int](1))
+        val bcast = b.add(Broadcast[Int](2))
+
+        source ~> merge ~> Flow[Int].map { s => println(s); s } ~> bcast ~> Sink.ignore
+                  merge.preferred              <~                  bcast
+        ClosedShape
+      })
+      //#unfair
+      // format: ON
+    }
+
+    "include a dropping cycle" in {
+      // format: OFF
+      //#dropping
+      RunnableGraph.fromGraph(GraphDSL.create() { implicit b =>
+        import GraphDSL.Implicits._
+
+        val merge = b.add(Merge[Int](2))
+        val bcast = b.add(Broadcast[Int](2))
+
+        source ~> merge ~> Flow[Int].map { s => println(s); s } ~> bcast ~> Sink.ignore
+            merge <~ Flow[Int].buffer(10, OverflowStrategy.dropHead) <~ bcast
+        ClosedShape
+      })
+      //#dropping
+      // format: ON
+    }
+
+    "include a dead zipping cycle" in {
+      // format: OFF
+      //#zipping-dead
+      // WARNING! The graph below never processes any elements
+      RunnableGraph.fromGraph(GraphDSL.create() { implicit b =>
+        import GraphDSL.Implicits._
+
+        val zip = b.add(ZipWith[Int, Int, Int]((left, right) => right))
+        val bcast = b.add(Broadcast[Int](2))
+
+        source ~> zip.in0
+        zip.out.map { s => println(s); s } ~> bcast ~> Sink.ignore
+        zip.in1             <~                bcast
+        ClosedShape
+      })
+      //#zipping-dead
+      // format: ON
+    }
+
+    "include a live zipping cycle" in {
+      // format: OFF
+      //#zipping-live
+      RunnableGraph.fromGraph(GraphDSL.create() { implicit b =>
+        import GraphDSL.Implicits._
+
+        val zip = b.add(ZipWith((left: Int, right: Int) => left))
+        val bcast = b.add(Broadcast[Int](2))
+        val concat = b.add(Concat[Int]())
+        val start = Source.single(0)
+
+        source ~> zip.in0
+        zip.out.map { s => println(s); s } ~> bcast ~> Sink.ignore
+        zip.in1 <~ concat <~ start
+                   concat         <~          bcast
+        ClosedShape
+      })
+      //#zipping-live
+      // format: ON
+    }
+
+  }
+
+}