docs(README): add pipx install instructions #17

	name: pre-commit

	on:
	pull_request:
	push:
	branches:
	- main
	jobs:
	pre-commit:
	name: pre-commit
	runs-on: ubuntu-latest
	steps:
	- name: Checkout repo
	uses: actions/checkout@v4
	with:
	fetch-depth: 0
	clean: false
	ref: ${{ github.head_ref }}

	- name: Set up Python
	uses: actions/setup-python@v5
	with:
	python-version: '3.8'
	cache: 'pip'
	# N.B. we don't need all the dependencies to run the code for just pre-commit
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	pip install -r requirements-dev.txt

	- name: Cache pre-commit envs
	uses: actions/cache@v2
	with:
	path: ~/.cache/pre-commit
	key: ${{ runner.os }}-pre-commit-${{ hashFiles('/requirements-dev.txt') }}-${{ hashFiles('/.pre-commit-config.yaml') }}
	restore-keys: \|
	${{ runner.os }}-pre-commit-${{ hashFiles('**/requirements-dev.txt') }}-
	${{ runner.os }}-pre-commit-

	- name: Run pre-commit
	env:
	REF_BEFORE: ${{ github.event_name == 'pull_request' && github.base_ref \|\| github.event.before }}
	REF_AFTER: ${{ github.event_name == 'pull_request' && github.head_ref \|\| github.event.after }}
	run: \|
	# make sure dropped commits are fetched
	git fetch origin $REF_BEFORE:$REF_BEFORE
	# if it's a push, check since the common ancestor of the before/after (for forced pushes)
	if [[ "${{ github.event_name }}" == "push" ]]; then
	export REF_BEFORE=$(git merge-base $REF_BEFORE $REF_AFTER)
	fi
	# make sure gitlint knows which commits to lint
	export GITLINT_COMMITS=$REF_BEFORE..$REF_AFTER
	# run pre-commit
	pre-commit run --from-ref $REF_BEFORE --to-ref $REF_AFTER

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