Vendor dependencies

Let's see how I like this workflow.

vendor/thiserror/tests/test_option.rs

@@ -0,0 +1,108 @@
+#![cfg_attr(
+    thiserror_nightly_testing,
+    feature(error_generic_member_access, provide_any)
+)]
+
+#[cfg(thiserror_nightly_testing)]
+pub mod structs {
+    use std::backtrace::Backtrace;
+    use thiserror::Error;
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptSourceNoBacktrace {
+        #[source]
+        source: Option<anyhow::Error>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptSourceAlwaysBacktrace {
+        #[source]
+        source: Option<anyhow::Error>,
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct NoSourceOptBacktrace {
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct AlwaysSourceOptBacktrace {
+        source: anyhow::Error,
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptSourceOptBacktrace {
+        #[source]
+        source: Option<anyhow::Error>,
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+}
+
+#[cfg(thiserror_nightly_testing)]
+pub mod enums {
+    use std::backtrace::Backtrace;
+    use thiserror::Error;
+
+    #[derive(Error, Debug)]
+    pub enum OptSourceNoBacktrace {
+        #[error("...")]
+        Test {
+            #[source]
+            source: Option<anyhow::Error>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptSourceAlwaysBacktrace {
+        #[error("...")]
+        Test {
+            #[source]
+            source: Option<anyhow::Error>,
+            backtrace: Backtrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum NoSourceOptBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum AlwaysSourceOptBacktrace {
+        #[error("...")]
+        Test {
+            source: anyhow::Error,
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptSourceOptBacktrace {
+        #[error("...")]
+        Test {
+            #[source]
+            source: Option<anyhow::Error>,
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+}
+
+#[test]
+#[cfg_attr(not(thiserror_nightly_testing), ignore)]
+fn test_option() {}