Add definition for Sigstore's DSSE signature extension #275

	#
	# Copyright 2022 The Sigstore Authors.
	#
	# 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: Check generated code for changes

	permissions:
	contents: read

	on:
	push:
	paths:
	- '**.proto'
	- 'gen/**'
	pull_request:
	paths:
	- '**.proto'
	- 'gen/**'

	jobs:
	check_generated_protos:
	name: Check generated protobufs
	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1

	# clear out the generated files directory so we know we are actually
	# generating all the files again (instead of a subset)
	- name: Clear out protobuf directory
	run: \|
	make clean

	- name: Compile protobufs
	run: \|
	make all

	- name: Ensure no files were modified as a result of the codegen
	run: git update-index --refresh && git diff-index --quiet HEAD -- \|\| git diff --exit-code

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