Vendor dependencies

Let's see how I like this workflow.

vendor/lock_api/src/lib.rs

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+// Copyright 2018 Amanieu d'Antras
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
+// http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+//! This library provides type-safe and fully-featured `Mutex` and `RwLock`
+//! types which wrap a simple raw mutex or rwlock type. This has several
+//! benefits: not only does it eliminate a large portion of the work in
+//! implementing custom lock types, it also allows users to write code which is
+//! generic with regards to different lock implementations.
+//!
+//! Basic usage of this crate is very straightforward:
+//!
+//! 1. Create a raw lock type. This should only contain the lock state, not any
+//!    data protected by the lock.
+//! 2. Implement the `RawMutex` trait for your custom lock type.
+//! 3. Export your mutex as a type alias for `lock_api::Mutex`, and
+//!    your mutex guard as a type alias for `lock_api::MutexGuard`.
+//!    See the [example](#example) below for details.
+//!
+//! This process is similar for RwLocks, except that two guards need to be
+//! exported instead of one. (Or 3 guards if your type supports upgradable read
+//! locks, see [extension traits](#extension-traits) below for details)
+//!
+//! # Example
+//!
+//! ```
+//! use lock_api::{RawMutex, Mutex, GuardSend};
+//! use std::sync::atomic::{AtomicBool, Ordering};
+//!
+//! // 1. Define our raw lock type
+//! pub struct RawSpinlock(AtomicBool);
+//!
+//! // 2. Implement RawMutex for this type
+//! unsafe impl RawMutex for RawSpinlock {
+//!     const INIT: RawSpinlock = RawSpinlock(AtomicBool::new(false));
+//!
+//!     // A spinlock guard can be sent to another thread and unlocked there
+//!     type GuardMarker = GuardSend;
+//!
+//!     fn lock(&self) {
+//!         // Note: This isn't the best way of implementing a spinlock, but it
+//!         // suffices for the sake of this example.
+//!         while !self.try_lock() {}
+//!     }
+//!
+//!     fn try_lock(&self) -> bool {
+//!         self.0
+//!             .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
+//!             .is_ok()
+//!     }
+//!
+//!     unsafe fn unlock(&self) {
+//!         self.0.store(false, Ordering::Release);
+//!     }
+//! }
+//!
+//! // 3. Export the wrappers. This are the types that your users will actually use.
+//! pub type Spinlock<T> = lock_api::Mutex<RawSpinlock, T>;
+//! pub type SpinlockGuard<'a, T> = lock_api::MutexGuard<'a, RawSpinlock, T>;
+//! ```
+//!
+//! # Extension traits
+//!
+//! In addition to basic locking & unlocking functionality, you have the option
+//! of exposing additional functionality in your lock types by implementing
+//! additional traits for it. Examples of extension features include:
+//!
+//! - Fair unlocking (`RawMutexFair`, `RawRwLockFair`)
+//! - Lock timeouts (`RawMutexTimed`, `RawRwLockTimed`)
+//! - Downgradable write locks (`RawRwLockDowngradable`)
+//! - Recursive read locks (`RawRwLockRecursive`)
+//! - Upgradable read locks (`RawRwLockUpgrade`)
+//!
+//! The `Mutex` and `RwLock` wrappers will automatically expose this additional
+//! functionality if the raw lock type implements these extension traits.
+//!
+//! # Cargo features
+//!
+//! This crate supports three cargo features:
+//!
+//! - `owning_ref`: Allows your lock types to be used with the `owning_ref` crate.
+//! - `arc_lock`: Enables locking from an `Arc`. This enables types such as `ArcMutexGuard`. Note that this
+//!   requires the `alloc` crate to be present.
+
+#![no_std]
+#![warn(missing_docs)]
+#![warn(rust_2018_idioms)]
+
+#[macro_use]
+extern crate scopeguard;
+
+#[cfg(feature = "arc_lock")]
+extern crate alloc;
+
+/// Marker type which indicates that the Guard type for a lock is `Send`.
+pub struct GuardSend(());
+
+/// Marker type which indicates that the Guard type for a lock is not `Send`.
+pub struct GuardNoSend(*mut ());
+
+unsafe impl Sync for GuardNoSend {}
+
+mod mutex;
+pub use crate::mutex::*;
+
+mod remutex;
+pub use crate::remutex::*;
+
+mod rwlock;
+pub use crate::rwlock::*;