docker: add basic docker support

Signed-off-by: Maciej Pijanowski <maciej.pijanowski@3mdeb.com>

The problem with building for non-host arch as described in the:
go-debos#9 was resolved. Basic
arm64 example image building was tested on the Ubuntu 18.04.
This may enable more users to take advantage of the debos, as
usning it on non-Debian distros seems either impossible ot not
trivial.

docker/Dockerfile

@@ -0,0 +1,55 @@
+### first stage - builder ###
+FROM golang:1.10 as builder
+
+MAINTAINER Maciej Pijanowski <maciej.pijanowski@3mdeb.com>
+
+ENV HOME=/scratch
+
+# install debos build dependencies
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    libglib2.0-dev \
+    libostree-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN go get -d github.com/go-debos/debos/cmd/debos
+WORKDIR /go/src/github.com/go-debos/debos/
+# RUN dep ensure
+RUN GOOS=linux go build -a cmd/debos/debos.go
+
+### second stage - runner ###
+FROM debian:stretch-slim as runner
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+# debos runtime dependencies
+# ca-certificates is required to validate HTTPS certificates when getting debootstrap release file
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    debootstrap \
+    libostree-1-1 \
+    ca-certificates \
+    systemd-container \
+    binfmt-support \
+    patch \
+    # fakemachine runtime dependencies
+    qemu-system-x86 \
+    qemu-user-static \
+    busybox \
+    linux-image-amd64 \
+    systemd \
+    dbus \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=builder /go/src/github.com/go-debos/debos/debos /usr/bin/debos
+
+# Bug description: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=806780
+# It was fixed in debootstrap 1.0.96 while Stretch provides 1.0.89
+COPY files/0001-Fix-multiple-components-usage-for-foreign.patch /usr/share/debootstrap
+RUN cd /usr/share/debootstrap && \
+    patch < 0001-Fix-multiple-components-usage-for-foreign.patch && \
+    rm /usr/share/debootstrap/0001-Fix-multiple-components-usage-for-foreign.patch && \
+    apt-get autoremove -y patch && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /root

docker/README.md

@@ -0,0 +1,22 @@
+Building
+--------
+
+```
+./build.sh
+```
+
+Prerequisites
+-------------
+
+* `binfmt_misc` module loaded on the host machine:
+
+```
+modprobe binfmt_misc
+```
+
+Running
+-------
+
+```
+./run.sh DEBOS_PARAMETERS
+```

docker/build.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+docker build -t debos .

docker/files/0001-Fix-multiple-components-usage-for-foreign.patch

@@ -0,0 +1,50 @@
+>From 6621d8304cb79dcc6e07098caaf6eaa56fe8594a Mon Sep 17 00:00:00 2001
+From: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
+Date: Tue, 1 Dec 2015 09:09:07 +0100
+Subject: [PATCH] Fix multiple components usage for --foreign
+
+commit e24e4b006736734e, bug #757819 made resolve_deps and
+setup_available in the --foreign case. However this only worked when
+using just one component as the USE_COMPONENTS variable is | delimited.
+
+Translate the USE_COMPONENTS variable on the fly from | delimited to
+space delimeted to allow multiple components to work again.
+
+Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
+---
+ functions | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/functions b/functions
+index 8bef5e6..64d76e4 100644
+--- a/functions
++++ b/functions
+@@ -1256,14 +1256,14 @@ resolve_deps () {
+ 	local ALLPKGS2="";
+ 	while [ "$PKGS" != "" ]; do
+ 		local NEWPKGS=""
+-		for c in ${COMPONENTS:-$USE_COMPONENTS}; do
++		for c in ${COMPONENTS:-$(echo ${USE_COMPONENTS} | tr '|' ' ')}; do
+ 			local path="dists/$SUITE/$c/binary-$ARCH/Packages"
+ 			local pkgdest="$TARGET/$($DLDEST pkg "$SUITE" "$c" "$ARCH" "$m1" "$path")"
+ 			NEWPKGS="$NEWPKGS $("$PKGDETAILS" GETDEPS "$pkgdest" $PKGS)"
+ 		done
+ 		PKGS=$(echo "$PKGS $NEWPKGS" | tr ' ' '\n' | sort | uniq)
+ 		local REALPKGS=""
+-		for c in ${COMPONENTS:-$USE_COMPONENTS}; do
++		for c in ${COMPONENTS:-$(echo ${USE_COMPONENTS} | tr '|' ' ')}; do
+ 			local path="dists/$SUITE/$c/binary-$ARCH/Packages"
+ 			local pkgdest="$TARGET/$($DLDEST pkg "$SUITE" "$c" "$ARCH" "$m1" "$path")"
+ 			REALPKGS="$REALPKGS $("$PKGDETAILS" PKGS REAL "$pkgdest" $PKGS | sed -n 's/ .*REAL.*$//p')"
+@@ -1279,7 +1279,7 @@ resolve_deps () {
+ setup_available () {
+ 	local m1="${MIRRORS%% *}"
+
+-	for c in ${COMPONENTS:-$USE_COMPONENTS}; do
++	for c in ${COMPONENTS:-$(echo ${USE_COMPONENTS} | tr '|' ' ')}; do
+ 		local path="dists/$SUITE/$c/binary-$ARCH/Packages"
+ 		local pkgdest="$TARGET/$($DLDEST pkg "$SUITE" "$c" "$ARCH" "$m1" "$path")"
+ 		# XXX: What if a package is in more than one component?
+-- 
+2.6.2
+

docker/run.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+docker run --rm \
+	-it \
+	--privileged \
+	-v ${PWD}:/root \
+	debos \
+	/bin/bash -c "debos $*"