add compat downgrader #854

	name: CI
	on:
	push:
	branches: [master, main]
	tags: ["*"]
	pull_request:
	jobs:
	test:
	name: Julia ${{ matrix.version }} - t=${{ matrix.threads }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ github.event_name }}
	runs-on: ${{ matrix.os }}
	strategy:
	fail-fast: false
	matrix:
	version:
	- '1'
	os:
	- ubuntu-latest
	threads:
	- '1'
	- '5'
	arch:
	- x64
	include:
	- os: ubuntu-latest
	arch: x64
	version: '1.9'
	threads: 2
	steps:
	- uses: actions/checkout@v4
	- uses: julia-actions/setup-julia@v1
	with:
	version: ${{ matrix.version }}
	arch: ${{ matrix.arch }}
	- uses: actions/cache@v3
	env:
	cache-name: cache-artifacts
	with:
	path: ~/.julia/artifacts
	key: ${{ runner.os }}-test-${{ env.cache-name }}-${{ hashFiles('**/Project.toml') }}
	restore-keys: \|
	${{ runner.os }}-test-${{ env.cache-name }}-
	${{ runner.os }}-test-
	${{ runner.os }}-
	- uses: cjdoris/julia-downgrade-compat-action@v1
	if: ${{ matrix.version == '1.9' }}
	with:
	skip: Pkg, InteractiveUtils, Random, LinearAlgebra
	- uses: julia-actions/julia-buildpkg@v1
	- uses: julia-actions/julia-runtest@v1
	env:
	JULIA_NUM_THREADS: ${{ matrix.threads }}
	- uses: julia-actions/julia-processcoverage@v1
	- uses: codecov/codecov-action@v3
	with:
	file: lcov.info
	docs:
	name: Documentation
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	- uses: julia-actions/setup-julia@v1
	with:
	version: '1'
	- uses: julia-actions/julia-buildpkg@v1
	- uses: julia-actions/julia-docdeploy@v1
	env:
	GKSwstype: nul # Fix for Plots with GR backend.
	GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
	DOCUMENTER_KEY: ${{ secrets.DOCUMENTER_KEY }}

Provide feedback