docker: add distfiles+checksum

srcpkgs/docker/template

@@ -1,7 +1,7 @@
 # Template file for 'docker'
 pkgname=docker
 version=1.7.1
-revision=1
+revision=2
 hostmakedepends="git go"
 makedepends="libbtrfs-devel sqlite-devel device-mapper-devel"
 short_desc="Pack, ship and run any application as a lightweight container"
@@ -15,11 +15,12 @@ depends="iptables xz git"
 nostrip=yes
 nocross=yes
 
-do_fetch() {
-	git clone -b v${version} git://github.com/docker/docker ${pkgname}-${version}
-}
+distfiles="https://github.com/$pkgname/$pkgname/archive/v$version.tar.gz"
+checksum=9cd26415d68a88d3cf576e7e78c2fe97f42af795404f552728acc5b41dccf4ef
+
 do_build() {
 	export AUTO_GOPATH=1
+	export DOCKER_GITCOMMIT=v$version
 	./hack/make.sh dynbinary
 }
 do_install() {