roles/prepare-gerrit-repos/tasks/repo.yaml

- name: Prepare project
  debug:
    msg: "{{ project.name }} {{ project_dest }}"

- name: Check if zuul.branch exists in repo
  set_fact:
    # If zuul checked out the branch we're testing, then it exists.
    project_branch_exists: "{{ zuul.branch == project.checkout }}"

- name: Check if repo has a dependent change
  set_fact:
    repo_has_dependent_change: "{{ zuul['items'] | selectattr('project.canonical_name', 'eq', zuul.project.canonical_name) | list | length | bool }}"

- name: Check for unsatisfiable source repo condition
  when:
    - "project.canonical_name != zuul.project.canonical_name"
    - "not project_branch_exists"
    - "repo_has_dependent_change"
  fail:
    msg: >-
      The repository {{ project.name }} does not contain the branch
      under test ({{ zuul.branch }}), but this change depends on a
      change to that project and branch.  While Zuul is able to check
      out the repos in the requested state, the branch mismatch means
      that Gerrit's submodule subscription would not automatically
      update the submodule pointer, and the merged state would not
      reflect the tested state.

      This configuration would be testable by creating a {{
      zuul.branch }} branch in the {{ project.name }} repo.
      Alternatively, you can merge the dependent change, manually
      update the submodule pointer, then test this change again.

# If there is no matching branch we need to check out the actual sha
# defined in the parent repo.
- name: Update submodule
  when: "not project_branch_exists"
  command: "git submodule update --init {{ project.name }}"
  args:
    chdir: "{{ gerrit_root }}"

- name: Move repo into place
  when: "project_branch_exists"
  command: "mv -T -f {{ ansible_user_dir }}/{{ project.src_dir }} {{ gerrit_root }}/{{ project_dest }}"