Update CONTRIBUTING.md now that toolstate.toml is gone.

Author: kennytm

CONTRIBUTING.md

@@ -345,26 +345,29 @@ Currently building Rust will also build the following external projects:
 
 * [clippy](https://github.com/rust-lang-nursery/rust-clippy)
 * [miri](https://github.com/solson/miri)
+* [rustfmt](https://github.com/rust-lang-nursery/rustfmt)
+* [rls](https://github.com/rust-lang-nursery/rls/)
 
-If your changes break one of these projects, you need to fix them by opening
-a pull request against the broken project asking to put the fix on a branch.
-Then you can disable the tool building via `src/tools/toolstate.toml`.
-Once the branch containing your fix is likely to be merged, you can point
-the affected submodule at this branch.
+We allow breakage of these tools in the nightly channel. Maintainers of these
+projects will be notified of the breakages and should fix them as soon as
+possible.
 
-Don't forget to also add your changes with
+After the external is fixed, one could add the changes with
 
-```
+```sh
 git add path/to/submodule
 ```
 
 outside the submodule.
 
-In order to prepare your PR, you can run the build locally by doing
+In order to prepare your tool-fixing PR, you can run the build locally by doing
 `./x.py build src/tools/TOOL`. If you will be editing the sources
 there, you may wish to set `submodules = false` in the `config.toml`
 to prevent `x.py` from resetting to the original branch.
 
+Breakage is not allowed in the beta and stable channels, and must be addressed
+before the PR is merged.
+
 #### Breaking Tools Built With The Compiler
 [breaking-tools-built-with-the-compiler]: #breaking-tools-built-with-the-compiler
 
@@ -382,12 +385,12 @@ tests.
 That means that, in the default state, you can't update the compiler without first
 fixing rustfmt, rls and the other tools that the compiler builds.
 
-Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/pull/45243)
-to make all of this easy to handle. The idea is that you mark the tools as "broken",
+Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/issues/45861)
+to make all of this easy to handle. The idea is that we allow these tools to be "broken",
 so that the rust-lang/rust build passes without trying to build them, then land the change
 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
-and the tools are working again, you go back in the compiler and change the tools back
-from "broken".
+and the tools are working again, you go back in the compiler and update the tools
+so they can be distributed again.
 
 This should avoid a bunch of synchronization dances and is also much easier on contributors as
 there's no need to block on rls/rustfmt/other tools changes going upstream.
@@ -406,15 +409,10 @@ Here are those same steps in detail:
 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
    merged because CI will be broken. You'll want to write a message on the PR referencing
    your change, and how the PR should be merged once your change makes it into a nightly.
-5. Update `src/tools/toolstate.toml` to indicate that the tool in question is "broken",
-   that will disable building it on CI. See the documentation in that file for the exact
-   configuration values you can use.
-6. Commit the changes to `src/tools/toolstate.toml`, **do not update submodules in your commit**,
-   and then update the PR you have for rust-lang/rust.
-7. Wait for your PR to merge.
-8. Wait for a nightly
-9. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
-10. (optional) Send a PR to rust-lang/rust updating the submodule, reverting `src/tools/toolstate.toml` back to a "building" or "testing" state.
+5. Wait for your PR to merge.
+6. Wait for a nightly
+7. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
+8. (optional) Send a PR to rust-lang/rust updating the submodule.
 
 #### Updating submodules
 [updating-submodules]: #updating-submodules
@@ -446,14 +444,14 @@ failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --ma
 If you haven't used the `[patch]`
 section of `Cargo.toml` before, there is [some relevant documentation about it
 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
-addition to that, you should read the 
+addition to that, you should read the
 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
 section of the documentation as well.
 
 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
 
 > Next up we need to ensure that our lock file is updated to use this new version of uuid so our project uses the locally checked out copy instead of one from crates.io. The way [patch] works is that it'll load the dependency at ../path/to/uuid and then whenever crates.io is queried for versions of uuid it'll also return the local version.
-> 
+>
 > This means that the version number of the local checkout is significant and will affect whether the patch is used. Our manifest declared uuid = "1.0" which means we'll only resolve to >= 1.0.0, < 2.0.0, and Cargo's greedy resolution algorithm also means that we'll resolve to the maximum version within that range. Typically this doesn't matter as the version of the git repository will already be greater or match the maximum version published on crates.io, but it's important to keep this in mind!
 
 This says that when we updated the submodule, the version number in our