Document MSRV policy #605

	name: Public API Check

	on:
	pull_request:
	branches:
	- master

	concurrency:
	# Cancels pending runs when a PR gets updated.
	group: ${{ github.workflow }}-${{ github.head_ref \|\| github.run_id }}
	cancel-in-progress: true

	# The workflow may fail if we change the public API in a pull request.
	# We allow fail on this action. But we should manually check if the changes are reasonable when we see a failed action.
	# It would be good if the workflow returns a neutral status when we find API changes. But it is currently not
	# possible with Github actions.
	jobs:
	check-public-api-changes:
	runs-on: ubuntu-latest
	steps:
	# Full git history needed
	- uses: actions/checkout@v2
	with:
	fetch-depth: 0

	# Install nightly
	- uses: actions-rs/toolchain@v1
	with:
	# We need nightly for cargo-public-api to get the API output.
	toolchain: nightly-2023-01-04
	profile: minimal
	# It is not necessary to use nightly as default (which is used to install cargo-public-api and compile our code).
	# However, our current toolchain is 1.59.0, and cargo-public-api requires 1.60 at least. To make it simple,
	# we just use the latest nightly toolchain.
	override: true
	- run: cargo --version

	# Install cargo-public-api
	- name: Install cargo-public-api
	run: cargo install cargo-public-api --version 0.26.0
	- name: API Diff
	run: cargo public-api diff origin/${GITHUB_BASE_REF}..${{ github.event.pull_request.head.sha }} --deny=all

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