[cheriot] Perform explicit ccache trimming in CI jobs #17

	name: Check coding style
	on: [pull_request]
	defaults:
	run:
	shell: bash
	jobs:
	check-format:
	runs-on: ubuntu-latest
	steps:
	- name: Checkout
	uses: actions/checkout@v2
	- name: Try to fetch required commits
	run: \|
	set -xe
	echo "base_ref=${{ github.base_ref }}"
	echo "github.event.pull_request.head.sha=${{ github.event.pull_request.head.sha }}"
	# Based on https://stackoverflow.com/questions/54181901/fetching-only-the-range-of-commits-not-present-in-base-branch
	for ((depth = 8; depth <= 65536; depth *= 2)); do
	echo "trying depth $depth ..."
	git fetch "--depth=$depth" origin "${{ github.base_ref }}:${{ github.base_ref }}"
	git fetch "--depth=$depth" origin "+${{ github.event.pull_request.head.sha }}"
	if git merge-base "${{ github.base_ref }}" "${{ github.event.pull_request.head.sha }}"; then
	echo "found with depth=$depth"
	break
	fi
	done
	- name: List commits
	run: git log --oneline "${{ github.base_ref }}..${{ github.event.pull_request.head.sha }}"
	- name: Run clang-format
	uses: wolletd/clang-format-checker@v1
	with:
	source-ref: "${{ github.event.pull_request.head.sha }}"
	target-ref: "${{ github.base_ref }}" # required, merge target

Provide feedback