Move Go code to src/cmd

This does not get everything where we want it finally, see #1266
nor the optimal way of building, but it gets it out of top level.

Added instructions to build if you have a Go installation.

Not moving `vendor` yet.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

Makefile

@@ -4,7 +4,7 @@ all: default
 
 GO_COMPILE=mobylinux/go-compile:3afebc59c5cde31024493c3f91e6102d584a30b9@sha256:e0786141ea7df8ba5735b63f2a24b4ade9eae5a02b0e04c4fca33b425ec69b0a
 
-MOBY_DEPS=$(wildcard *.go) pkg vendor
+MOBY_DEPS=$(wildcard src/cmd/moby/*.go)
 GOOS=$(shell uname -s | tr '[:upper:]' '[:lower:]')
 GOARCH=amd64
 ifneq ($(GOOS),linux)
@@ -12,7 +12,7 @@ CROSS=-e GOOS=$(GOOS) -e GOARCH=$(GOARCH)
 endif
 
 bin/moby: $(MOBY_DEPS) | bin
-	tar cf - $(MOBY_DEPS) | docker run --rm --net=none --log-driver=none -i $(CROSS) $(GO_COMPILE) --package github.com/docker/moby -o $@ | tar xf -
+	tar cf - vendor src/initrd src/pad4 -C src/cmd/moby . | docker run --rm --net=none --log-driver=none -i $(CROSS) $(GO_COMPILE) --package github.com/docker/moby -o $@ | tar xf -
 
 moby-initrd.img: bin/moby moby.yaml
 	$^

README.md

@@ -20,6 +20,10 @@ Moby, a toolkit for building custom minimal, immutable Linux distributions.
 Simple build instructions: use `make` to build.
 This will build the Moby customisation tool and a Moby initrd image.
 
+If you already have a Go build environment and installed the source in your `GOPATH`
+you can do `go install github.com/docker/moby/cmd/moby` to install the `moby` tool
+instead, and then use `moby moby.yaml` to build the example configuration.
+
 #### Build requirements
 
 - GNU `make`

src/cmd/moby/main.go

@@ -12,7 +12,7 @@ import (
 	"os/exec"
 	"path/filepath"
 
-	"github.com/docker/moby/pkg/initrd"
+	"github.com/docker/moby/src/initrd"
 )
 
 const (

src/initrd/initrd.go

@@ -7,7 +7,7 @@ import (
 	"errors"
 	"io"
 
-	"github.com/docker/moby/pkg/pad4"
+	"github.com/docker/moby/src/pad4"
 	"github.com/surma/gocpio"
 )