优化对称差集，交集实现 #578

	# Copyright 2021 ecodeclub
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	name: changelog

	on:
	pull_request:
	types: [opened, synchronize, reopened, labeled, unlabeled]
	branches:
	- develop
	- main
	- dev

	jobs:
	changelog:
	runs-on: ubuntu-latest
	if: "!contains(github.event.pull_request.labels.*.name, 'Skip Changelog')"

	steps:
	- uses: actions/checkout@v2

	- name: Check for CHANGELOG changes
	run: \|
	# Only the latest commit of the feature branch is available
	# automatically. To diff with the base branch, we need to
	# fetch that too (and we only need its latest commit).
	git fetch origin ${{ github.base_ref }} --depth=1
	if [[ $(git diff --name-only FETCH_HEAD \| grep CHANGELOG) ]]
	then
	echo "A CHANGELOG was modified. Looks good!"
	else
	echo "No CHANGELOG was modified."
	echo "Please add a CHANGELOG entry, or add the \"Skip Changelog\" label if not required."
	false
	fi

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