Add chart diffing GHA workflow #16

	name: Diff chart changes
	on:
	pull_request:
	types: [opened, reopened, synchronize]
	concurrency:
	group: ${{ github.workflow }}-${{ github.repository }}-${{ github.ref_name }}
	cancel-in-progress: false

	jobs:
	render-charts-base:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	with:
	fetch-depth: 0
	ref: ${{ github.event.pull_request.base.ref }}
	show-progress: false
	- name: Run govuk-app-render
	run: ./govuk-app-render.sh
	- name: Archive rendered charts
	uses: actions/upload-artifact@v4
	with:
	name: rendered-charts-base
	path: output/
	retention-days: 1
	render-charts-head:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	with:
	fetch-depth: 0
	ref: ${{ github.event.pull_request.head.ref }}
	show-progress: false
	- name: Run govuk-app-render
	run: ./govuk-app-render.sh
	- name: Archive rendered charts
	uses: actions/upload-artifact@v4
	with:
	name: rendered-charts-head
	path: output/
	retention-days: 1
	diff-charts:
	runs-on: ubuntu-latest
	needs: [render-charts-base, render-charts-head]
	permissions:
	pull-requests: write
	steps:
	- uses: actions/checkout@v4
	with:
	fetch-depth: 0
	ref: ${{ github.event.pull_request.head.ref }}
	show-progress: false
	- uses: actions/download-artifact@v4
	with:
	name: rendered-charts-base
	path: base-r/
	- uses: actions/download-artifact@v4
	with:
	name: rendered-charts-head
	path: head-r/
	- name: Diff charts and comment on PR
	env:
	GH_TOKEN: ${{ github.token }}
	PR_URL: ${{ github.event.pull_request.html_url }}
	run: ./create-diff-pr.sh

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