Add container image building

Makefile

@@ -336,6 +336,7 @@ install-build-tools:
 
 define build_release
 	$(eval GITREF ?= $(shell git describe --exact-match --tags HEAD 2>/dev/null || git symbolic-ref --short HEAD 2>/dev/null || git rev-parse --short HEAD))
+	@echo "GITREF=$(GITREF)"
 	./buildtools/build-release \
 		--target=$(1) \
 		$(if $(CLEANUP),--cleanup) \
@@ -364,6 +365,11 @@ release-static:
 release-tarball:
 	$(call build_release,"tarball")
 
+container:
+	$(eval GITREF ?= $(shell git describe --exact-match --tags HEAD 2>/dev/null || git symbolic-ref --short HEAD 2>/dev/null || git rev-parse --short HEAD))
+	@echo "GITREF=$(GITREF)"
+	./buildtools/build-containerimage "$(GITREF)"
+
 .PHONY: tags
 tags:
 	rm -fv TAGS

buildtools/build-containerimage

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+GIT_BRANCH="${1:-master}"
+
+podman \
+    build \
+    --squash \
+    --no-cache \
+    --force-rm \
+    --build-arg="GIT_REPO=file:///mnt" \
+    --build-arg="BRANCH=${GIT_BRANCH}" \
+    -v "${PWD}":/mnt:ro \
+    -f "buildtools/containerimage/Containerfile" \
+    --tag "mergerfs:${GIT_BRANCH}" \
+    buildtools/

buildtools/containerimage/Containerfile

@@ -0,0 +1,19 @@
+FROM --platform=linux/amd64 alpine:latest as build
+
+ARG GIT_REPO
+ARG BRANCH
+
+RUN <<EOF
+    apk add git gcc g++ make linux-headers
+    git clone --single-branch --branch="${BRANCH}" "${GIT_REPO}" /tmp/mergerfs
+    cd /tmp/mergerfs
+    make NDEBUG=1 LTO=1 STATIC=1 DESTDIR=/tmp/install -j$(nproc) install
+    tar cvfz /tmp/mergerfs.tgz --directory=/tmp/install usr sbin
+EOF
+
+FROM --platform=linux/amd64 alpine:latest
+RUN --mount=from=build,source=/tmp/mergerfs.tgz,target=/tmp/mergerfs.tgz <<EOF
+    tar xvf /tmp/mergerfs.tgz -C /
+EOF
+ENTRYPOINT ["/usr/local/bin/mergerfs"]
+CMD ["--help"]