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",
+    ],
+)