Cleanup otp/elixir matrix #807

	name: CI

	on: push

	# Set the GITHUB_TOKEN to a restricted permission we don't need anything else than this.
	# This will disable all other permissions than metadata: read, which is always enabled.
	permissions:
	contents: read

	jobs:
	test:
	runs-on: ubuntu-latest
	name: OTP ${{ matrix.otp }} / Elixir ${{ matrix.elixir }}
	strategy:
	matrix:
	otp: ["25.3.2.8", "26.2.1"]
	elixir: ["1.14.5", "1.15.7", "1.16.1"]
	include:
	- otp: "25.3.2.8"
	elixir: "1.13.4"
	env:
	MIX_ENV: test
	cache_version: v2
	steps:
	- uses: actions/checkout@v2
	name: Checkout

	- uses: actions/cache@v1
	name: Cache deps
	with:
	path: deps
	key: deps--${{ env.cache_version }}${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-${{ hashFiles('mix.lock') }}
	restore-keys: \|
	deps-${{ env.cache_version }}-${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}

	- uses: actions/cache@v1
	name: Cache _build
	with:
	path: _build
	key: build-erlef-${{ env.cache_version }}-${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-${{ hashFiles('mix.lock') }}
	restore-keys: \|
	build-erlef-${{ env.cache_version }}-${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}

	- uses: erlef/setup-elixir@v1
	name: Setup elixir
	with:
	otp-version: ${{matrix.otp}}
	elixir-version: ${{matrix.elixir}}

	- run: mix deps.get

	- name: Check that no unused deps exist
	run: \|
	mix deps.clean --unused --unlock
	git diff --exit-code

	- run: mix compile
	- run: mix test --trace --include skip
	- run: mix credo
	- run: mix dialyzer
	- run: mix format --check-formatted

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