better upgrade method - use "latest" switch

defaults/main.yml

@@ -1,19 +1,15 @@
 ---
 dockerpy: no
+
 docker_proxy: no
 docker_http_proxy: ""
 docker_https_proxy: ""
 docker_no_proxy: ""
+
+docker_version: "17.06"
+#docker_version: "latest"
 docker_upgrade: false
+
 docker_default_config:
   storage-driver: devicemapper
   log-level: info
-
-docker_version: "17.06"
-docker_setup_script_url: "https://releases.rancher.com/install-docker/{{ docker_version }}.sh"
-
-# DANGER! THIS VALUE IS USED TO VERIFY THAT THE DOCKER SETUP SCRIPT IS LEGITIMATE.
-# DO NOT MODIFY THIS UNLESS YOU HAVE SPECIFIED A DIFFERENT "docker_version" or "setup_script_url"
-# IF YOU HAVE GENERATED AN MD5 CHECKSUM FOR YOUR DESIRED SETUP SCRIPT, STORE IT IN THIS VARIABLE
-# IF YOU REALLY DON'T WANT TO VERIFY CHECKSUM, SET THIS VALUE TO "false" or "no"
-docker_setup_script_md5_sum: "6be324016277879d49bd0e7f9f91e546"

tasks/install.yml

@@ -18,8 +18,8 @@
 
 - name: Install docker
   package:
-    name: "{{ docker_package | default('docker-ce') }}"
-    state: present
+    name: "{{ docker_package }}"
+    state: "{{ (docker_version == 'latest') | ternary('latest', 'present') }}"
     update_cache: yes
   register: __ret
   retries: 10

tasks/preflight.yml

@@ -22,3 +22,8 @@
 - name: apply default daemon config
   set_fact:
     docker_json: "{{ docker_default_config | combine(docker_config | default({})) }}"
+
+- name: update docker (backwards compatibility flag)
+  set_fact:
+    docker_version: latest
+  when: docker_upgrade

vars/debian.yml

@@ -1,3 +1,4 @@
+docker_package: "docker-ce{{ (docker_version != 'latest') | ternary('=' ~ docker_version, '') }}"
 docker_dependencies:
   - apt-transport-https
   - ca-certificates

vars/redhat.yml

@@ -1,3 +1,4 @@
+grafana_package: "docker-ce{{ (docker_version != 'latest') | ternary('-' ~ docker_version, '') }}"
 docker_dependencies:
   - ca-certificates
   - yum-utils