move command implementations to internal/

internal/cmdrootfs/BUILD

@@ -0,0 +1,13 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["cmdrootfs.go"],
+    importpath = "github.com/motiejus/code/undocker/internal/cmdrootfs",
+    visibility = ["//src/undocker:__subpackages__"],
+    deps = [
+        "//src/undocker/rootfs:go_default_library",
+        "@com_github_jessevdk_go_flags//:go_default_library",
+        "@org_uber_go_multierr//:go_default_library",
+    ],
+)

internal/cmdrootfs/cmdrootfs.go

@@ -0,0 +1,43 @@
+package cmdrootfs
+
+import (
+	"errors"
+	"os"
+
+	goflags "github.com/jessevdk/go-flags"
+	"github.com/motiejus/code/undocker/rootfs"
+	"go.uber.org/multierr"
+)
+
+type CmdRootFS struct {
+	PositionalArgs struct {
+		Infile  goflags.Filename `long:"infile" description:"Input tarball"`
+		Outfile string           `long:"outfile" description:"Output path, stdout is '-'"`
+	} `positional-args:"yes" required:"yes"`
+}
+
+func (r *CmdRootFS) Execute(args []string) (err error) {
+	if len(args) != 0 {
+		return errors.New("too many args")
+	}
+
+	in, err := os.Open(string(r.PositionalArgs.Infile))
+	if err != nil {
+		return err
+	}
+	defer func() { err = multierr.Append(err, in.Close()) }()
+
+	var out *os.File
+	outf := string(r.PositionalArgs.Outfile)
+	if outf == "-" {
+		out = os.Stdout
+	} else {
+		out, err = os.Create(outf)
+		if err != nil {
+			return err
+		}
+	}
+	defer func() { err = multierr.Append(err, out.Close()) }()
+
+	return rootfs.RootFS(in, out)
+}