Update students' PR stats #1079

	name: Update students' PR stats
	# Updates ./stats/pr-stats.md on every push to main/master.
	# Changes are pushed directly to main/master.
	# Relies on GH actions logic that prevents action to trigger itself.
	#
	# Q1: Why not `on pull_request: types: [closed] branches: [master, main]` + `if: github.event.pull_request.merged == true`?
	# A1: Apparently workflows on PRs from forks are run in the context of forks
	# where github actor has no sufficient privileges to push to the base repo.
	#
	# Uses GitHub CLI app provided by GitHub runner.
	on:
	schedule:
	- cron: '37 22 * * *'
	jobs:
	update-pr-stats:
	runs-on: ubuntu-latest
	steps:
	- name: Pull source code
	uses: actions/checkout@v2
	with:
	path: './'
	- name: Update stats file
	run: \|
	cd ./stats
	gh --version
	node make-stats.js
	cd ..
	env:
	GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
	# Publish to the default branch in current repo using GITHUB_TOKEN and other default settings.
	- name: Setup git credentials
	uses: oleksiyrudenko/gha-git-credentials@rc
	with:
	token: '${{ secrets.GITHUB_TOKEN }}'
	- name: Commit and publish update
	# consider ${{ '"$..."' }} pattern to escape $-sequence that should reach bash
	run: \|
	if [ -n "$(git status --porcelain)" ]; then
	TIMESTAMP=`date "+%Y-%m-%d %H:%M:%S %Z"`;
	git add ./stats/pr-stats.md;
	git commit -m "Stats: update stats/pr-stats.md as of $TIMESTAMP";
	git push;
	else
	echo "Nothing to commit and push";
	fi

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