Add mirror-workspace-git-repos role

Change-Id: I6958e95a9ea31ab8ae027a9b33069d74be615d91

roles/mirror-workspace-git-repos/README.rst

@@ -0,0 +1,6 @@
+Mirror the local git repos to remote nodes
+
+This role uses git operations (unlike :zuul:role:`prepare-workspace`
+which uses rsync) to mirror the local prepared git repos to the remote
+nodes.  This may be useful if the remote node already has a copy of
+some or all of the git repos.

roles/mirror-workspace-git-repos/tasks/main.yaml

@@ -0,0 +1,19 @@
+- name: Synchronize src repos to workspace directory
+  command: "git push --mirror git+ssh://{{ ansible_user }}@{{ ansible_host }}/{{ ansible_user_dir }}/{{ item.src_dir}}"
+  chdir: "{{ zuul.executor.src_root }}/{{ item.src_dir }}"
+  with_items: "{{ zuul.projects }}"
+  delegate_to: localhost
+
+- name: Determine local HEAD
+  shell: "git status |head -1 |awk '{ print $NF }'"
+  chdir: "{{ zuul.executor.src_root }}/{{ item.src_dir }}"
+  with_items: "{{ zuul.projects }}"
+  delegate_to: localhost
+  register: statuses
+
+- name: Checkout local HEAD on remote
+  command: "git checkout {{ item.1 }}"
+  chdir: "{{ zuul.executor.src_root }}/{{ item.0.src_dir }}"
+  with_together:
+    - "{{ zuul.projects }}"
+    - "{{ statuses }}"