diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..eb5a316
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+target
diff --git a/Cargo.toml b/Cargo.toml
index 0c5a19d..bc0cac5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,10 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
-rustc_middle = { path = "../rustc_middle" }
-rustc_driver = { path = "../rustc_driver" }
-rustc_borrowck = { path = "../rustc_borrowck" }
-rustc_interface = { path = "../rustc_interface" }
+rustc_middle = { path = "../rustc_middle", optional = true }
+rustc_driver = { path = "../rustc_driver", optional = true }
+rustc_borrowck = { path = "../rustc_borrowck", optional = true }
+rustc_interface = { path = "../rustc_interface", optional = true }
+
+[features]
+default = ["rustc_middle", "rustc_driver", "rustc_borrowck", "rustc_interface"]
diff --git a/README.md b/README.md
index de35894..ae49098 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,18 @@ sync is pushed entirely onto us, without affecting rustc workflows negatively.
 This may change in the future, but changes to policy should only be done via a
 compiler team MCP.
 
+## Instructions for working on this crate locally
+
+Since the crate is the same in the rustc repo and here, the dependencies on rustc_* crates
+will only either work here or there, but never in both places at the same time. Thus we use
+optional dependencies on the rustc_* crates, requiring local development to use
+
+```
+cargo build --no-default-features -Zavoid-dev-deps
+```
+
+in order to compile successfully.
+
 ## Instructions for syncing
 
 ### Updating this repository
@@ -19,8 +31,38 @@ git subtree push --prefix=compiler/rustc_smir url_to_your_fork_of_project_stable
 
 and then open a PR of your `some_feature_branch` against https://github.com/rust-lang/project-stable-mir
 
-### Updating the rustc librar
+### Updating the rustc library
+
+First we need to bump our stack limit, as the rustc repo otherwise quickly hits that:
+
+```
+ulimit -s 60000
+```
+
+#### Maximum function recursion depth (1000) reached
+
+Then we need to disable `dash` as the default shell for sh scripts, as otherwise we run into a
+hard limit of a recursion depth of 1000:
+
+```
+sudo dpkg-reconfigure dash
+```
+
+and then select `No` to disable dash.
+
+
+#### Patching your `git worktree`
+
+The regular git worktree does not scale to repos of the size of the rustc repo.
+So download the `git-subtree.sh` from https://github.com/gitgitgadget/git/pull/493/files and run
+
+```
+sudo cp --backup /path/to/patched/git-subtree.sh /usr/lib/git-core/git-subtree
+sudo chmod --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
+sudo chown --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
+```
 
+#### Actually doing a sync
 
 In the rustc repo, execute
 
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..7b696fc
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,3 @@
+[toolchain]
+channel = "nightly-2022-06-01"
+components = [ "rustfmt", "rustc-dev" ]
diff --git a/src/lib.rs b/src/lib.rs
index 405ee13..decdae9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,10 +1,18 @@
 //! The WIP stable interface to rustc internals.
+//!
+//! For more information see https://github.com/rust-lang/project-stable-mir
+//!
+//! # Note
+//!
+//! This API is still completely unstable and subject to change.
 
 #![doc(
     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
     test(attr(allow(unused_variables), deny(warnings)))
 )]
 
+#![cfg_attr(not(feature = "default"), feature(rustc_private))]
+
 pub mod mir;
 
 pub mod very_unstable;
diff --git a/src/mir.rs b/src/mir.rs
index 97969be..855605b 100644
--- a/src/mir.rs
+++ b/src/mir.rs
@@ -1,4 +1,4 @@
-pub use rustc_middle::mir::{
+pub use crate::very_unstable::middle::mir::{
     visit::MutVisitor, AggregateKind, AssertKind, BasicBlock, BasicBlockData, BinOp, BindingForm,
     BlockTailInfo, Body, BorrowKind, CastKind, ClearCrossCrate, Constant, ConstantKind,
     CopyNonOverlapping, Coverage, FakeReadCause, Field, GeneratorInfo, ImplicitSelfKind,
diff --git a/src/very_unstable.rs b/src/very_unstable.rs
index dacdabf..12ba133 100644
--- a/src/very_unstable.rs
+++ b/src/very_unstable.rs
@@ -3,12 +3,25 @@
 //! Only use rustc_smir in your dependencies and use the reexports here instead of
 //! directly referring to the unstable crates.
 
-pub use rustc_borrowck as borrowck;
-pub use rustc_driver as driver;
-pub use rustc_hir as hir;
-pub use rustc_interface as interface;
-pub use rustc_middle as middle;
-pub use rustc_mir_dataflow as dataflow;
-pub use rustc_mir_transform as transform;
-pub use rustc_serialize as serialize;
-pub use rustc_trait_selection as trait_selection;
+macro_rules! crates {
+    ($($rustc_name:ident -> $name:ident,)*) => {
+        $(
+            #[cfg(not(feature = "default"))]
+            pub extern crate $rustc_name as $name;
+            #[cfg(feature = "default")]
+            pub use $rustc_name as $name;
+        )*
+    }
+}
+
+crates! {
+    rustc_borrowck -> borrowck,
+    rustc_driver -> driver,
+    rustc_hir -> hir,
+    rustc_interface -> interface,
+    rustc_middle -> middle,
+    rustc_mir_dataflow -> dataflow,
+    rustc_mir_transform -> transform,
+    rustc_serialize -> serialize,
+    rustc_trait_selection -> trait_selection,
+}