Add a 'base-minimal' job with it's set of playbooks

The 'base-minimal' job has for purpose to be what we consider to be
the smallest possible set of roles/tasks to be applied on nodes
regardless of the job context.

Inheriting from this minimal job provides the ability to run roles
or tasks that would have otherwise been included by default only on
a need basis.

Change-Id: I5c255a6f9d2adb91fbc222742bd2249f126ca982

playbooks/base-minimal/README.rst

@@ -0,0 +1,8 @@
+base-minimal
+------------
+
+These playbooks are used to select a minimal subset of the roles included in
+the base playbooks.
+
+It will do nothing else than what is explicitely necessary for any job to run
+properly.

playbooks/base-minimal/post-logs.yaml

@@ -0,0 +1,9 @@
+- hosts: localhost
+  roles:
+    - role: add-fileserver
+      fileserver: "{{ site_logs }}"
+
+- hosts: "{{ site_logs.fqdn }}"
+  roles:
+    - role: upload-logs
+      zuul_log_url: "http://logs.openstack.org"

playbooks/base-minimal/post-ssh.yaml

@@ -0,0 +1,3 @@
+- hosts: all
+  roles:
+    - remove-build-sshkey

playbooks/base-minimal/pre.yaml

@@ -0,0 +1,4 @@
+- hosts: all
+  roles:
+    - add-build-sshkey
+    - start-zuul-console

zuul.yaml

@@ -169,6 +169,29 @@
     secrets:
       - site_logs
 
+- job:
+    name: base-minimal
+    parent: null
+    description: |
+      A subset of what the 'base' job provides: the absolute minimum considered
+      required to run for any one job.
+      It doesn't set up cached git repositories, will not set up mirrors,
+      doesn't validate the node and does not generate an ARA report.
+      These tasks, if required, can be included by the dependant jobs
+      themselves on a need basis.
+    pre-run: playbooks/base-minimal/pre
+    post-run:
+      - playbooks/base-minimal/post-ssh
+      - playbooks/base-minimal/post-logs
+    roles:
+      - zuul: openstack-infra/zuul-jobs
+    timeout: 1800
+    nodes:
+      - name: ubuntu-xenial
+        label: ubuntu-xenial
+    secrets:
+      - site_logs
+
 - job:
     name: base-test
     parent: null