Vendor dependencies

Let's see how I like this workflow.

vendor/tokio-stream/tests/stream_merge.rs

@@ -0,0 +1,83 @@
+use tokio_stream::{self as stream, Stream, StreamExt};
+use tokio_test::task;
+use tokio_test::{assert_pending, assert_ready};
+
+mod support {
+    pub(crate) mod mpsc;
+}
+
+use support::mpsc;
+
+#[tokio::test]
+async fn merge_sync_streams() {
+    let mut s = stream::iter(vec![0, 2, 4, 6]).merge(stream::iter(vec![1, 3, 5]));
+
+    for i in 0..7 {
+        let rem = 7 - i;
+        assert_eq!(s.size_hint(), (rem, Some(rem)));
+        assert_eq!(Some(i), s.next().await);
+    }
+
+    assert!(s.next().await.is_none());
+}
+
+#[tokio::test]
+async fn merge_async_streams() {
+    let (tx1, rx1) = mpsc::unbounded_channel_stream();
+    let (tx2, rx2) = mpsc::unbounded_channel_stream();
+
+    let mut rx = task::spawn(rx1.merge(rx2));
+
+    assert_eq!(rx.size_hint(), (0, None));
+
+    assert_pending!(rx.poll_next());
+
+    tx1.send(1).unwrap();
+
+    assert!(rx.is_woken());
+    assert_eq!(Some(1), assert_ready!(rx.poll_next()));
+
+    assert_pending!(rx.poll_next());
+    tx2.send(2).unwrap();
+
+    assert!(rx.is_woken());
+    assert_eq!(Some(2), assert_ready!(rx.poll_next()));
+    assert_pending!(rx.poll_next());
+
+    drop(tx1);
+    assert!(rx.is_woken());
+    assert_pending!(rx.poll_next());
+
+    tx2.send(3).unwrap();
+    assert!(rx.is_woken());
+    assert_eq!(Some(3), assert_ready!(rx.poll_next()));
+    assert_pending!(rx.poll_next());
+
+    drop(tx2);
+    assert!(rx.is_woken());
+    assert_eq!(None, assert_ready!(rx.poll_next()));
+}
+
+#[test]
+fn size_overflow() {
+    struct Monster;
+
+    impl tokio_stream::Stream for Monster {
+        type Item = ();
+        fn poll_next(
+            self: std::pin::Pin<&mut Self>,
+            _cx: &mut std::task::Context<'_>,
+        ) -> std::task::Poll<Option<()>> {
+            panic!()
+        }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            (usize::MAX, Some(usize::MAX))
+        }
+    }
+
+    let m1 = Monster;
+    let m2 = Monster;
+    let m = m1.merge(m2);
+    assert_eq!(m.size_hint(), (usize::MAX, None));
+}