Fix for C++20 #32

	name: Clang format

	on: [pull_request]

	jobs:
	clang-format:
	# We need at least 20.04 to install clang-format-11.
	runs-on: ubuntu-20.04
	steps:
	- uses: actions/checkout@v2
	with:
	ref: ${{ github.event.pull_request.head.sha }}
	- name: Install prerequisites
	env:
	DEBIAN_FRONTEND: noninteractive
	run: \|
	sudo apt update -y
	sudo apt install -y clang-format-11
	sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-11 100
	sudo update-alternatives --install /usr/bin/git-clang-format git-clang-format /usr/bin/git-clang-format-11 100
	- name: Run clang-format on changed files
	run: \|
	set -x
	git fetch origin ${{ github.event.pull_request.base.ref }}
	git fetch origin pull/${{ github.event.pull_request.number }}/head:${{ github.event.pull_request.head.ref }}
	BASE_COMMIT=$(git rev-parse ${{ github.event.pull_request.base.sha }})
	COMMIT_FILES=$(git diff --diff-filter=d --name-only ${BASE_COMMIT} \| grep -E -- '\.cxx\|\.h' \| grep -i -v LinkDef) \|\| true ;# avoid failures if nothing is greped
	[ "X$COMMIT_FILES" = X ] && { echo "No files to check" ; exit 0; }
	RESULT_OUTPUT=$(git-clang-format --commit ${BASE_COMMIT} --diff ${COMMIT_FILES})
	if [ "$RESULT_OUTPUT" == "no modified files to format" ] \|\| [ "$RESULT_OUTPUT" == "clang-format did not modify any files" ]; then
	echo "clang-format passed."
	exit 0
	else
	git-clang-format --commit $BASE_COMMIT --diff
	echo "$RESULT_OUTPUT"
	echo "clang-format failed."
	exit 1
	fi

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