Add help strings for `-a`/`-r` in `sub`/`gsub`/`ssub` #2804

	name: Miller-Go

	on:
	push:
	branches: [ main ]
	pull_request:
	branches: [ main ]

	jobs:

	build:
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	os: [ubuntu-latest, macos-latest, windows-latest]

	steps:
	- uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683

	- name: Set up Go
	uses: actions/setup-go@41dfa10bad2bb2ae585af6ee5bb4d7d973ad74ed
	with:
	go-version: 1.19

	- name: Build
	run: make build

	- name: Unit tests
	run: make unit-test

	- name: Regression tests
	# We run these with a convoluted path to ensure the tests don't
	# rely on a specific invocation
	run: test/../mlr regtest -S

	- name: PrepareArtifactNonWindows
	if: matrix.os != 'windows-latest'
	run: mkdir -p bin/${{matrix.os}} && cp mlr bin/${{matrix.os}}

	- name: PrepareArtifactWindows
	if: matrix.os == 'windows-latest'
	run: mkdir -p bin/${{matrix.os}} && cp mlr.exe bin/${{matrix.os}}

	- uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882
	with:
	name: mlr-${{matrix.os}}
	path: bin/${{matrix.os}}/*

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