feat(stdlib): add fold function #1999

	# Changelog
	#
	# Validates that a changelog entry was added.
	# Runs on PRs when:
	# - opened/re-opened
	# - new commits pushed
	# - label is added or removed
	# Runs on merge queues, but just passes, because it is a required check.

	name: Changelog

	on:
	pull_request:
	types: [opened, synchronize, reopened, labeled, unlabeled]
	# Due to merge queue requiring same status checks as PRs, must pass by default
	merge_group:
	types: [checks_requested]

	jobs:
	validate-changelog:
	runs-on: ubuntu-latest
	if: github.event_name == 'pull_request'
	env:
	PR_HAS_LABEL: ${{ contains( github.event.pull_request.labels.*.name, 'no-changelog') }}
	steps:
	# checkout full depth because in the check_changelog_fragments script, we need to specify a
	# merge base. If we only shallow clone the repo, git may not have enough history to determine
	# the base.
	- uses: actions/checkout@v4
	with:
	fetch-depth: 0

	- run: \|
	if [[ $PR_HAS_LABEL == 'true' ]] ; then
	echo "'no-changelog' label detected."
	exit 0
	fi

	# helper script needs to reference the master branch to compare against
	git fetch origin main:refs/remotes/origin/main

	./scripts/check_changelog_fragments.sh

	check-changelog:
	name: Changelog
	runs-on: ubuntu-latest
	needs: validate-changelog
	if: always()
	env:
	FAILED: ${{ contains(needs.*.result, 'failure') }}
	steps:
	- name: exit
	run: \|
	echo "failed=${{ env.FAILED }}"
	if [[ "$FAILED" == "true" ]] ; then
	exit 1
	else
	exit 0
	fi

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