Register built-in engine commands at runtime instead of compile-time

This allows selective loading of commands, and paves the way to dynamic
plugins.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

builtins/builtins.go

@@ -0,0 +1,40 @@
+package builtins
+
+import (
+	"github.com/dotcloud/docker/engine"
+
+	"github.com/dotcloud/docker"
+	"github.com/dotcloud/docker/api"
+	"github.com/dotcloud/docker/networkdriver/lxc"
+)
+
+func Register(eng *engine.Engine) {
+	daemon(eng)
+	remote(eng)
+}
+
+// remote: a RESTful api for cross-docker communication
+func remote(eng *engine.Engine) {
+	eng.Register("serveapi", api.ServeApi)
+}
+
+// daemon: a default execution and storage backend for Docker on Linux,
+// with the following underlying components:
+//
+// * Pluggable storage drivers including aufs, vfs, lvm and btrfs.
+// * Pluggable execution drivers including lxc and chroot.
+//
+// In practice `daemon` still includes most core Docker components, including:
+//
+// * The reference registry client implementation
+// * Image management
+// * The build facility
+// * Logging
+//
+// These components should be broken off into plugins of their own.
+//
+func daemon(eng *engine.Engine) {
+	eng.Register("initserver", docker.InitServer)
+	eng.Register("init_networkdriver", lxc.InitDriver)
+	eng.Register("version", docker.GetVersion)
+}