beacon-node-builds: add README, remove unused batches

Signed-off-by: Jakub Sokołowski <jakub@status.im>

ansible/roles/beacon-node-builds/README.md

@@ -0,0 +1,31 @@
+# Description
+
+This role configures a set of Systemd timers that build configured branches of [nimbus-eth2]() and push the built docker images.
+
+# Configuration
+
+The minimal configuration would look something like:
+```yaml
+# Branch to build and frequency
+beacon_node_builds_branches:
+  - name: 'xyz'
+    branch: 'feature/xyz'
+    frequency: '*-*-* 02:00:00'
+
+# Required to push Docker images
+beacon_node_builds_docker_hub_user: 'docker-hub-user'
+beacon_node_builds_docker_hub_token: 'super-secret-password'
+```
+
+# Management
+
+You can check the status of the timers using:
+```
+ > sudo systemctl list-timers 'beacon-node-build-*'
+NEXT                        LEFT          LAST                        PASSED       UNIT                           ACTIVATES                       
+Mon 2020-11-09 02:00:00 UTC 4h 12min left Sun 2020-11-08 02:00:01 UTC 19h ago      beacon-node-build-master.timer beacon-node-build-master.service
+Mon 2020-11-09 10:00:00 UTC 12h left      Sun 2020-11-08 10:00:03 UTC 11h ago      beacon-node-build-devel.timer  beacon-node-build-devel.service 
+Mon 2020-11-09 18:00:00 UTC 20h left      Sun 2020-11-08 18:00:04 UTC 3h 47min ago beacon-node-build-libp2p.timer beacon-node-build-libp2p.service
+
+3 timers listed.
+```

ansible/roles/beacon-node-builds/defaults/main.yml

@@ -14,12 +14,9 @@ beacon_node_builds_branches:
   - name: 'master'
     branch: 'master'
     frequency: '*-*-* 02:00:00'
-    batches: [ 'a', 'b' ]
   - name: 'devel'
     branch: 'devel'
     frequency: '*-*-* 10:00:00'
-    batches: [ 'a', 'b' ]
   - name: 'libp2p'
     branch: 'nim-libp2p-auto-bump'
     frequency: '*-*-* 18:00:00'
-    batches: [ 'a', 'b' ]

ansible/roles/beacon-node-builds/tasks/build.yml

@@ -40,7 +40,6 @@
     group: 'adm'
     mode: 0644
 
-
 - name: Create timer for rebuilding image
   include_role: name=systemd-timer
   vars:

ansible/roles/beacon-node-builds/templates/build.sh.j2

@@ -9,7 +9,6 @@ if [[ "${USER}" != "{{ beacon_node_builds_user }}" ]]; then
 fi
 
 IMAGE="{{ beacon_node_builds_image_name }}:{{ item.name }}"
-BATCHES=({{ item.batches | join(" ") }})
 
 # Build the Beacon node binaries
 {