Document some additional points about maintaining rustfmt (#3579)

Processes.md

@@ -6,6 +6,7 @@ In this Section, we describe how to stabilise an option of the rustfmt's configr
 
 ## Conditions
 
+- Is the default value correct ?
 - The design and implementation of the option are sound and clean.
 - The option is well tested, both in unit tests and, optimally, in real usage.
 - There is no open bug about the option that prevents its use.
@@ -20,3 +21,36 @@ Open a pull request that closes the tracking issue. The tracking issue is listed
 ## After the stabilisation
 
 The option should remain backward-compatible with previous parameters of the option. For instance, if the option is an enum `enum Foo { Alice, Bob }` and the variant `Foo::Bob` is removed/renamed, existing use of the `Foo::Bob` variant should map to the new logic. Breaking changes can be applied under the condition they are version-gated.
+
+# Make a Release
+
+## 0. Update CHANGELOG.md
+
+## 1. Update Cargo.toml and Cargo.lock
+
+For example, 1.0.0 -> 1.0.1:
+
+```diff
+-version = "1.0.0"
++version = "1.0.1"
+```
+
+## 2. Push the commit to the master branch
+
+E.g., https://github.com/rust-lang/rustfmt/commit/5274b49caa1a7db6ac10c76bf1a3d5710ccef569
+
+## 3. Create a release tag
+
+```sh
+git tag -s v1.2.3 -m "Release 1.2.3"
+```
+
+## 4. Publish to crates.io
+
+`cargo publish`
+
+## 5. Create a PR to rust-lang/rust to update the rustfmt submodule
+
+Note that if you are updating `rustc-ap-*` crates, then you need to update **every** submodules in the rust-lang/rust repository that depend on the crates to use the same version of those.
+
+As of 2019/05, there are two such crates: `rls` and `racer` (`racer` depends on `rustc-ap-syntax` and `rls` depends on `racer`, and `rls` is one of submodules of the rust-lang/rust repository).