add test script to execute ghwc in docker+snapshot

Adds a test script (hack/run-against-snapshot.sh) that builds the ghwc
binary into a Docker image, extracts a snapshot created by ghwc-snapshot
into a tmpdir, and runs the ghwc Docker image after bind-mounting the
snapshot tmpdir as /host.

This allows us to test ghw against a snapshot static filesystem from a
user's machine (Linux only for now)

Issue #66

Dockerfile

@@ -0,0 +1,26 @@
+FROM golang:1.13-stretch as builder
+WORKDIR /go/src/github.com/jaypipes/ghw
+
+# Force the go compiler to use modules.
+ENV GO111MODULE=on
+ENV GOPROXY=direct
+
+# go.mod and go.sum go into their own layers.
+COPY go.mod .
+COPY go.sum .
+
+# This ensures `go mod download` happens only when go.mod and go.sum change.
+RUN go mod download
+
+COPY . .
+
+RUN CGO_ENABLED=0 go build -o ghwc ./cmd/ghwc/
+
+FROM alpine:3.7
+RUN apk add --no-cache ethtool
+
+WORKDIR /bin
+
+COPY --from=builder /go/src/github.com/jaypipes/ghw/ghwc /bin
+
+CMD ghwc

cmd/ghw-snapshot/main.go

@@ -1,3 +1,4 @@
+// +build linux
 //
 // Use and distribution licensed under the Apache license version 2.
 //

hack/run-against-snapshot.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+SNAPSHOT_FILEPATH=${SNAPSHOT_FILEPATH:-$1}
+
+if [[ ! -f $SNAPSHOT_FILEPATH ]]; then
+    echo "Cannot find snapshot file. Please call $0 with path to snapshot or set SNAPSHOT_FILEPATH envvar."
+    exit 1
+fi
+
+root_dir=$(cd "$(dirname "$0").."; pwd)
+ghwc_image_name="ghwc"
+local_git_version=$(git describe --tags --always --dirty)
+IMAGE_VERSION=${IMAGE_VERSION:-$local_git_version}
+
+snap_tmp_dir=$(mktemp -d -t ghw-snap-test-XXX)
+
+echo "extracting snapshot $SNAPSHOT_FILEPATH to $snap_tmp_dir ..."
+tar -xf $SNAPSHOT_FILEPATH -C $snap_tmp_dir
+
+echo "building Docker image with ghwc ..."
+
+docker build -f $root_dir/Dockerfile -t $ghwc_image_name:$IMAGE_VERSION $root_dir
+
+echo "running ghwc Docker image with volume mount to snapshot dir ..."
+
+docker run -it -v $snap_tmp_dir:/host -e GHW_CHROOT="/host" $ghwc_image_name:$IMAGE_VERSION