Add a toggle to enable saving the ARA sqlite database

It might be useful for jobs to save the ARA sqlite database, for
example for debugging purposes, or if they want to import and use
the database elsewhere.

Change-Id: Ie82b42c34dfe6173116d88cc174deda70c5aa9ad

roles/emit-ara-html/README.rst

@@ -12,6 +12,11 @@ Have ARA generate html logs if ARA and ARA data are both present.
    Whether to compress the ARA HTML output or not.
    Defaults to ``true``.
 
+.. zuul:rolevar:: ara_save_database
+
+   Whether the ARA sqlite database should be saved as part of the logs.
+   Defaults to ``false``.
+
 .. tip::
    Make sure the web server is configured to set the required mimetypes_ in
    order to serve gzipped content properly.

roles/emit-ara-html/defaults/main.yaml

@@ -3,3 +3,6 @@ ara_generate_html: true
 
 # Whether to compress the ARA HTML output or not
 ara_compress_html: true
+
+# Whether to save the ARA sqlite database as part of the logs or not
+ara_save_database: false

roles/emit-ara-html/tasks/main.yaml

@@ -3,6 +3,14 @@
     path: "{{ zuul.executor.work_root }}/.ara/ansible.sqlite"
   register: ara_db_stat
 
+- name: Save the ARA database
+  command: |
+    cp "{{ zuul.executor.work_root }}/.ara/ansible.sqlite" \
+    {{ zuul.executor.log_root }}
+  when:
+    - ara_db_stat.stat.exists
+    - ara_save_database | bool
+
 - name: Check for ARA install
   command: which ara
   ignore_errors: yes