Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/fs_link.rs

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+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support file operations
+
+use tokio::fs;
+
+use std::io::prelude::*;
+use std::io::BufReader;
+use tempfile::tempdir;
+
+#[tokio::test]
+async fn test_hard_link() {
+    let dir = tempdir().unwrap();
+    let src = dir.path().join("src.txt");
+    let dst = dir.path().join("dst.txt");
+
+    {
+        let mut file = std::fs::File::create(&src).unwrap();
+        file.write_all(b"hello").unwrap();
+    }
+
+    let dst_2 = dst.clone();
+
+    assert!(fs::hard_link(src, dst_2.clone()).await.is_ok());
+
+    let mut content = String::new();
+
+    {
+        let file = std::fs::File::open(dst).unwrap();
+        let mut reader = BufReader::new(file);
+        reader.read_to_string(&mut content).unwrap();
+    }
+
+    assert!(content == "hello");
+}
+
+#[cfg(unix)]
+#[tokio::test]
+async fn test_symlink() {
+    let dir = tempdir().unwrap();
+    let src = dir.path().join("src.txt");
+    let dst = dir.path().join("dst.txt");
+
+    {
+        let mut file = std::fs::File::create(&src).unwrap();
+        file.write_all(b"hello").unwrap();
+    }
+
+    let src_2 = src.clone();
+    let dst_2 = dst.clone();
+
+    assert!(fs::symlink(src_2.clone(), dst_2.clone()).await.is_ok());
+
+    let mut content = String::new();
+
+    {
+        let file = std::fs::File::open(dst.clone()).unwrap();
+        let mut reader = BufReader::new(file);
+        reader.read_to_string(&mut content).unwrap();
+    }
+
+    assert!(content == "hello");
+
+    let read = fs::read_link(dst.clone()).await.unwrap();
+    assert!(read == src);
+
+    let symlink_meta = fs::symlink_metadata(dst.clone()).await.unwrap();
+    assert!(symlink_meta.file_type().is_symlink());
+}