Add the possibility to set the dev container name

By using `make CONTAINER_NAME=docker-dev shell` you're able to name
the docker-dev container to what you want. The idea behind it is by
knowing the name of your dev container you can automate easily some
thing using `docker exec` later.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

Makefile

@@ -51,6 +51,9 @@ DOCKER_MOUNT := $(if $(BIND_DIR),-v "$(CURDIR)/$(BIND_DIR):/go/src/github.com/do
 # Note that `BIND_DIR` will already be set to `bundles` if `DOCKER_HOST` is not set (see above BIND_DIR line), in such case this will do nothing since `DOCKER_MOUNT` will already be set.
 DOCKER_MOUNT := $(if $(DOCKER_MOUNT),$(DOCKER_MOUNT),-v /go/src/github.com/docker/docker/bundles)
 
+# This allows to set the docker-dev container name
+DOCKER_CONTAINER_NAME := $(if $(CONTAINER_NAME),--name $(CONTAINER_NAME),)
+
 # enable package cache if DOCKER_INCREMENTAL_BINARY and DOCKER_MOUNT (i.e.DOCKER_HOST) are set
 PKGCACHE_MAP := gopath:/go/pkg goroot-linux_amd64_netgo:/usr/local/go/pkg/linux_amd64_netgo
 PKGCACHE_VOLROOT := dockerdev-go-pkg-cache
@@ -62,7 +65,7 @@ GIT_BRANCH_CLEAN := $(shell echo $(GIT_BRANCH) | sed -e "s/[^[:alnum:]]/-/g")
 DOCKER_IMAGE := docker-dev$(if $(GIT_BRANCH_CLEAN),:$(GIT_BRANCH_CLEAN))
 DOCKER_PORT_FORWARD := $(if $(DOCKER_PORT),-p "$(DOCKER_PORT)",)
 
-DOCKER_FLAGS := docker run --rm -i --privileged $(DOCKER_ENVS) $(DOCKER_MOUNT) $(DOCKER_PORT_FORWARD)
+DOCKER_FLAGS := docker run --rm -i --privileged $(DOCKER_CONTAINER_NAME) $(DOCKER_ENVS) $(DOCKER_MOUNT) $(DOCKER_PORT_FORWARD)
 BUILD_APT_MIRROR := $(if $(DOCKER_BUILD_APT_MIRROR),--build-arg APT_MIRROR=$(DOCKER_BUILD_APT_MIRROR))
 export BUILD_APT_MIRROR