[skip ci] Change release procedure to use cargo-release

Remove the example Cargo.toml entry from README.md because it's obvious,
and it creates extra work at release time.

Author: asomers

README.md

@@ -84,16 +84,10 @@ Tier 3:
   * x86_64-unknown-openbsd
   * x86_64-unknown-redox
 
-## Usage
+## Minimum Supported Rust Version (MSRV)
 
-`nix` requires Rust 1.46.0 or newer.
-
-To use `nix`, add this to your `Cargo.toml`:
-
-```toml
-[dependencies]
-nix = "0.22.0"
-```
+nix is supported on Rust 1.46.0 and higher.  It's MSRV will not be
+changed in the future without bumping the major or minor version.
 
 ## Contributing
 

RELEASE_PROCEDURE.md

@@ -3,38 +3,16 @@ library.
 
 # Before Release
 
-Based on changes since the last release, pick a new version number
-following semver conventions. For nix, a change that drops support for
-some Rust versions counts as a breaking change, and requires a major bump.
+Nix uses [cargo release](https://github.com/crate-ci/cargo-release) to automate
+the release process.  Based on changes since the last release, pick a new
+version number following semver conventions. For nix, a change that drops
+support for some Rust versions counts as a breaking change, and requires a
+major bump.
 
 The release is prepared as follows:
 
-- Ask for a new libc version if, necessary. It usually is.
-- Make a commit with a message like "Release v0.8.3" with the following
-  changes:
-  - In `CHANGELOG.md`, rename the Unreleased section to the new version
-    followed by the date of the release.
-  - Add a new Unreleased section header to `CHANGELOG.md` with the four
-    Added, Changed, Fixed, and Removed sections added.
-  - In `Cargo.toml`, update the version to the new version.
-  - In `Cargo.toml`, change the libc dependency to the latest version.
-  - In `README.md`, update the version in the Usage section to the new
-    version.
+- Ask for a new libc version if, necessary. It usually is.  Then update the
+  dependency in Cargo.toml accordingly.
 - Confirm that everything's ready for a release by running
-  `cargo publish --dry-run`
-- Make a pull request.
-- Once the PR is merged, tag the merge commit, e.g. `git tag v0.8.3
-  $MERGE_COMMIT_SHA1`.
-- Push the tag, e.g. `git push origin v0.8.3`.
-
-# Create Release
-
-- Checkout the tag.
-- Publish to crates.io with `cargo publish`.
-
-# After Release
-
-Once a release is done, all that's left is to change the `libc` version
-back to using the version from git. So make a pull request containing a
-simple commit entitled "Start the next dev cycle" that changes the `libc`
-dependency in `Cargo.toml` to using it from git master.
+  `cargo release --dry-run <patch|minor|major>`
+- Create the release with `cargo release <patch|minor|major>`

release.toml

@@ -0,0 +1,5 @@
+no-dev-version = true
+pre-release-replacements = [
+	{ file="CHANGELOG.md", search="Unreleased", replace="{{version}}" },
+	{ file="CHANGELOG.md", search="ReleaseDate", replace="{{date}}" }
+]