Build option to follow the latest stable on a release series/track

README.md

@@ -130,6 +130,7 @@ You can set the following environment variables prior to building:
  - KUBE_VERSION: kubernetes release to package. Defaults to latest stable.
  - ETCD_VERSION: version of etcd. Defaults to v3.3.4.
  - CNI_VERSION: version of CNI tools. Defaults to v0.6.0.
+ - KUBE_TRACK: kubernetes release series (e.g., 1.10) to package. Defaults to latest stable.
 
 For example:
 ```

build-scripts/prepare-env.sh

@@ -14,9 +14,14 @@ export KUBE_ARCH
 export ETCD_VERSION="${ETCD_VERSION:-v3.3.4}"
 export CNI_VERSION="${CNI_VERSION:-v0.6.0}"
 
+export KUBE_TRACK="${KUBE_TRACK:-}"
 export KUBE_SNAP_BINS="${KUBE_SNAP_BINS:-}"
 if [ -z "$KUBE_SNAP_BINS" ]; then
-  export KUBE_VERSION="${KUBE_VERSION:-`curl -L https://dl.k8s.io/release/stable.txt`}"
+  if [ -z "$KUBE_TRACK" ]; then
+    export KUBE_VERSION="${KUBE_VERSION:-`curl -L https://dl.k8s.io/release/stable.txt`}"
+  else
+    export KUBE_VERSION="${KUBE_VERSION:-`curl -L https://dl.k8s.io/release/stable-${KUBE_TRACK}.txt`}"
+  fi
 else
   export KUBE_VERSION=`cat $KUBE_SNAP_BINS/version`
 fi

snapcraft.yaml

 name: microk8s
 version-script: |
-  if [ -z "$KUBE_SNAP_BINS" ]; then
-    curl -L https://dl.k8s.io/release/stable.txt
-  else
-    cat $KUBE_SNAP_BINS/version
-  fi
+  . build-scripts/prepare-env.sh > /dev/null
+  echo $KUBE_VERSION
 version: "latest"
 summary: Kubernetes in your box.
 description: Microk8s deploys and configures all kubernetes services in a snap.