Merge pull request #4650 from vbatts/vbatts-btrfs_build_tags

btrfs: build tags

hack/PACKAGERS.md

@@ -160,15 +160,23 @@ export DOCKER_BUILDTAGS='apparmor'
 There are build tags for disabling graphdrivers as well. By default, support
 for all graphdrivers are built in.
 
-To disable devicemapper
+To disable btrfs:
+```bash
+export DOCKER_BUILDTAGS='exclude_graphdriver_btrfs'
+```
+
+To disable devicemapper:
 ```bash
 export DOCKER_BUILDTAGS='exclude_graphdriver_devicemapper'
 ```
-To disable aufs
+
+To disable aufs:
 ```bash
 export DOCKER_BUILDTAGS='exclude_graphdriver_aufs'
 ```
 
+NOTE: if you need to set more than one build tag, space separate them.
+
 ### Static Daemon
 
 If it is feasible within the constraints of your distribution, you should

runtime/runtime.go

@@ -16,7 +16,6 @@ import (
 	"github.com/dotcloud/docker/runtime/execdriver/execdrivers"
 	"github.com/dotcloud/docker/runtime/execdriver/lxc"
 	"github.com/dotcloud/docker/runtime/graphdriver"
-	_ "github.com/dotcloud/docker/runtime/graphdriver/btrfs"
 	_ "github.com/dotcloud/docker/runtime/graphdriver/vfs"
 	_ "github.com/dotcloud/docker/runtime/networkdriver/lxc"
 	"github.com/dotcloud/docker/runtime/networkdriver/portallocator"

runtime/runtime_btrfs.go

@@ -0,0 +1,7 @@
+// +build !exclude_graphdriver_btrfs
+
+package runtime
+
+import (
+	_ "github.com/dotcloud/docker/runtime/graphdriver/btrfs"
+)