misc: enhance support for replayable instances of `InputStream` #539

	name: API compatibility verification

	on:
	pull_request:
	types: [ opened, synchronize, reopened, labeled, unlabeled ]
	branches: [ main ]

	jobs:
	api-compat-verification:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- name: Check for API compatibility
	if: ${{ !contains(github.event.pull_request.labels.*.name, 'acknowledge-api-break') }}
	run: \|
	git fetch origin ${{ github.base_ref }} --depth 1 && \
	git diff remotes/origin/${{ github.base_ref }} --numstat "*.api" \| awk '
	BEGIN { s = 0 }

	# git diff numstat shows lines deleted in field 2, hence sum up field 2 across all items
	{ s += $2 }

	# exit with the number of lines deleted as the result code so that `if failure()` works below
	END { exit s }
	'
	- name: Error message
	if: ${{ failure() }}
	run: \|
	echo "::error ::This change modifies the public API in a way that may be backwards-incompatible. Carefully review this pull request and either:"
	echo "::error ::* Revert the changes which caused the API incompatibility –or–"
	echo "::error ::* Add the 'acknowledge-api-break' label to this PR (in rare cases warranting an API breakage)"
	exit 1

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