Add Dockerfile for mp3fs image

This also includes a Docker Compose configuration file and a README
explaining how to use Docker with mp3fs.

Makefile.am

@@ -55,7 +55,7 @@ staticcheck:
 # and the check is made automatically passing because the headers aren't
 # preserved properly.
 mdcheck:
-	@set -e ; for f in *.md ; do \
+	@set -e ; for f in *.md */*.md ; do \
 	    echo "Checking format for $$f." ; \
 	    if [ "$$f" = mp3fs.1.md ] ; then \
 	    	sed 's/\.\\/!./g' "$$f" | pandoc -d .pandocfmt.yaml -f markdown -t markdown | sed 's/!\./.\\/g' | diff -u $$f - || : ; \

docker/Dockerfile

@@ -0,0 +1,33 @@
+FROM debian:buster-slim AS base
+
+FROM base AS build
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    build-essential \
+    ca-certificates \
+    curl \
+    libflac++-dev \
+    libfuse-dev \
+    libid3tag0-dev \
+    libmp3lame-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN curl -sL https://github.com/khenriks/mp3fs/releases/download/v0.91/mp3fs-0.91.tar.gz | \
+    tar -xz && \
+    cd mp3fs-0.91 && \
+    ./configure && make && make install
+
+FROM base
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    fuse \
+    libflac++6v5 \
+    libid3tag0 \
+    libmp3lame0 \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=build /usr/local /usr/local
+
+RUN mkdir /music
+
+ENTRYPOINT ["mp3fs", "-d", "/music", "/mnt", "-oallow_other"]

docker/README.md

@@ -0,0 +1,55 @@
+# Docker Instructions
+
+There is now a [Docker
+image](https://hub.docker.com/repository/docker/khenriks/mp3fs) available for
+mp3fs. Most users will probably prefer to use the command normally, but it's
+available for those who want it.
+
+## docker run
+
+To use this with the `docker run` command, run:
+
+``` console
+$ docker run --device /dev/fuse \
+  --cap-add SYS_ADMIN \
+  --security-opt apparmor:unconfined \
+  -v /home/khenriks/Music:/music:ro \
+  -v /tmp/mp3:/mnt:shared \
+  khenriks/mp3fs \
+  -b 256
+```
+
+There's a lot here, so let's unpack the command.
+
+  - `docker run` is how you run a docker container.
+  - `--device /dev/fuse` is needed to allow FUSE access.
+  - `--cap-add SYS_ADMIN` is necessary to mount filesystems inside Docker
+    containers. This might not be needed in the future for FUSE (see
+    [docker/for-linux\#321](https://github.com/docker/for-linux/issues/321)),
+    but for now it's required.
+  - `--security-opt apparmor:unconfined` is also needed to mount filesystems
+    inside Docker.
+  - `-v /home/khenriks/Music:/music:ro` mounts the host directory
+    `/home/khenriks/Music` read-only in the container. This will be the input
+    for mp3fs. The host directory can be replaced with anything, but `/music`
+    is required because that's where the container expects it.
+  - `-v /tmp/mp3:/mnt:shared` mounts the directory `/tmp/mp3` inside the
+    container. This will be the output from mp3fs. Again, the host directory
+    can be anything, but `/mnt` is required by the container. `shared` makes
+    the mp3fs mount inside the container show up in the host directory outside.
+  - `khenriks/mp3fs` is the name of the Docker image.
+  - `-b 256` is the normal mp3fs flag for bitrate. You can use any mp3fs flags
+    here, after the image name.
+
+## Docker Compose
+
+There's also a `docker-compose.yml` file available, if that's your jam. To use
+it, run:
+
+``` console
+$ MUSICDIR=/home/khenriks/Music MP3DIR=/tmp/mp3 MP3FS_FLAGS="-b 256" \
+  docker-compose up
+```
+
+This will do the same thing as the previous command, but is hopefully simpler
+to use. `MUSICDIR`, `MP3DIR`, and `MP3FS_FLAGS` can be customized as desired.

docker/docker-compose.yml

@@ -0,0 +1,15 @@
+# Basic Docker Compose file for mp3fs
+version: '3'
+services:
+    mp3fs:
+        image: khenriks/mp3fs
+        devices:
+            - /dev/fuse
+        cap_add:
+            - SYS_ADMIN
+        security_opt:
+            - apparmor:unconfined
+        volumes:
+            - ${MUSICDIR}:/music:ro
+            - ${MP3DIR}:/mnt:shared
+        command: ${MP3FS_FLAGS}