Add support to pullin distgit changes

This change addes the ability to bundle a packaging change during the
dlrn build with a code change. It can also be used to just test
packaging changes by switching the change repo to be the main repository
and include a distgit change only.

Change-Id: Ibeea3ef436dccaf36c254b232f922983cd101c5b

roles/build-test-packages/README.md

@@ -39,6 +39,8 @@ Role Variables
 * `dlrn_use_local_mirrors` -- use the local repo definitions from
   /etc/yum.repos.d/ for CentOS and DLRN while building packages; used upstream
 
+
+Example artg_change_list for just code changes:
 ```yaml
 artg_change_list:
     - host: "review.openstack.org"
@@ -48,6 +50,20 @@ artg_change_list:
     - host: ...
 ```
 
+Example artg_change_list for code changes and package changes:
+```yaml
+artg_change_list:
+    - host: "review.openstack.org"
+      project: "openstack/tripleo-heat-templates"
+      branch: "master"
+      refspec: "refs/changes/1/123456/1"
+      distgit:
+          host: "ssh://user@review.rdoproject.org"
+          project: "openstack/tripleo-heat-templates-distgit"
+          refspec: "refs/changes/1/123456/1"
+    - host: ...
+```
+
 Gating with Zuul or Jenkins
 ---------------------------
 

roles/build-test-packages/tasks/dlrn-build.yml

@@ -64,6 +64,15 @@
         version: 'FETCH_HEAD'
       when: artg_repos_dir is not defined or copy_dir is failed
 
+    - name: Clone the distgit change
+      git:
+        repo: '{{ artg_change.distgit.host }}/{{ artg_change.distgit.project }}'
+        dest: '{{ build_repo_dir }}/DLRN/data/{{ project_name_mapped.stdout }}_distro'
+        refspec: '{{ artg_change.distgit.refspec }}'
+        version: 'FETCH_HEAD'
+        accept_hostkey: yes
+      when: artg_change.distgit is defined and (artg_repos_dir is not defined or copy_dir is failed)
+
     - name: Run DLRN
       shell: >
         set +e;