Vendor dependencies

Let's see how I like this workflow.

vendor/anyhow/tests/test_repr.rs

@@ -0,0 +1,29 @@
+mod drop;
+
+use self::drop::{DetectDrop, Flag};
+use anyhow::Error;
+use std::marker::Unpin;
+use std::mem;
+
+#[test]
+fn test_error_size() {
+    assert_eq!(mem::size_of::<Error>(), mem::size_of::<usize>());
+}
+
+#[test]
+fn test_null_pointer_optimization() {
+    assert_eq!(mem::size_of::<Result<(), Error>>(), mem::size_of::<usize>());
+}
+
+#[test]
+fn test_autotraits() {
+    fn assert<E: Unpin + Send + Sync + 'static>() {}
+    assert::<Error>();
+}
+
+#[test]
+fn test_drop() {
+    let has_dropped = Flag::new();
+    drop(Error::new(DetectDrop::new(&has_dropped)));
+    assert!(has_dropped.get());
+}