initial Antora boilerplate

Makefile

@@ -0,0 +1,54 @@
+pages   := $(shell find . -type f -name '*.adoc')
+web_dir := ./_public
+
+# Determine whether to use podman
+#
+# podman currently fails when executing in GitHub actions on Ubuntu LTS 20.04,
+# so we never use podman if GITHUB_ACTIONS==true.
+use_podman := $(shell command -v podman 2>&1 >/dev/null; p="$$?"; \
+		if [ "$${GITHUB_ACTIONS}" != "true" ]; then echo "$$p"; else echo 1; fi)
+
+ifeq ($(use_podman),0)
+	engine_cmd  ?= podman
+	engine_opts ?= --rm --tty --userns=keep-id
+else
+	engine_cmd  ?= docker
+	engine_opts ?= --rm --tty --user "$$(id -u)"
+endif
+
+# renovate: datasource=github-releases depName=vshn/antora
+antora_VERSION ?= 3.1.2.3
+antora_cmd  ?= $(engine_cmd) run $(engine_opts) --volume "$${PWD}":/antora ghcr.io/vshn/antora:$(antora_VERSION)
+
+# renovate: datasource=github-releases depName=vshn/antora-preview
+preview_VERSION ?= 3.1.2.3
+antora_opts ?= --cache-dir=.cache/antora
+preview_cmd ?= $(engine_cmd) run --rm --publish 35729:35729 --publish 2020:2020 --volume "${PWD}":/preview/antora ghcr.io/vshn/antora-preview:$(preview_VERSION) --antora=docs --style=vshn
+
+UNAME := $(shell uname)
+ifeq ($(UNAME), Linux)
+	OS = linux-x64
+	OPEN = xdg-open
+endif
+ifeq ($(UNAME), Darwin)
+	OS = darwin-x64
+	OPEN = open
+endif
+
+.PHONY: docs-clean
+clean:
+	rm -rf $(web_dir) .cache
+
+.PHONY: docs-open
+docs-open: $(web_dir)/index.html
+	-$(OPEN) $<
+
+.PHONY: docs-html
+docs-html:    $(web_dir)/index.html
+
+.PHONY: docs-preview
+docs-preview:
+	$(preview_cmd)
+
+$(web_dir)/index.html: playbook.yml $(pages)
+	$(antora_cmd) $(antora_opts) $<