Use sparse registry on nightly

Fixes #5

CHANGELOG.md

@@ -7,6 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.3.1] - 2022-08-14
+
+### Changed
+
+* Use the sparse-registry on nightly for faster access to the crate registry on nightly.
+    <https://internals.rust-lang.org/t/call-for-testing-cargo-sparse-registry/16862>
+
 ## [1.3.0] - 2022-07-30
 
 ### Added

action.yml

@@ -62,6 +62,9 @@ runs:
         echo "CARGO_TERM_COLOR=always" >> $GITHUB_ENV
         echo "RUST_BACKTRACE=short" >> $GITHUB_ENV
         echo "RUSTFLAGS=-D warnings" >> $GITHUB_ENV
+        # Enable faster sparse index on nightly
+        # https://internals.rust-lang.org/t/call-for-testing-cargo-sparse-registry/16862
+        echo "CARGO_UNSTABLE_SPARSE_REGISTRY=true" >> $GITHUB_ENV
       shell: bash
     - name: "Install Rust Problem Matcher"
       run: echo "::add-matcher::${{ github.action_path }}/rust.json"