Update requirements-check job to run on arbitrary targets

Update the requirements-check job to run on repos other than the
zuul.project, but keep that as the default.  Add the job as a check
and gate job to this repo, but targeting nova.  This allows us to
run the job on changes to its definition.

Change-Id: I67b818cdff01d29c62497826d4b4e3387c74e9e9
Depends-On: https://review.opendev.org/c/openstack/requirements/+/934249

.zuul.d/project-template.yaml

@@ -10,6 +10,21 @@
 - job:
     name: requirements-check
     parent: unittests
+    description: |
+      Check that requirements in the target repo match OpenStack
+      global requirements.
+
+      **Job Variables**
+
+      .. zuul:jobvar:: zuul_work_dir
+         :default: {{ zuul.project.src_dir }}
+
+         Directory holding the project to check.
+
+      .. zuul:jobvar:: zuul_branch
+         :default: {{ zuul.branch }}
+
+         Branch to check.
     # NOTE(gmann): Update the nodeset if we move testing to the new version
     # of ubuntu. We are explicitly setting the nodeset here because the base
     # job (unittests) moving to the ubuntu latest version can break this
@@ -28,3 +43,15 @@
       - ^doc/requirements.txt$
       - playbooks/requirements-check.yaml
       - ^lower-constraints.txt$
+
+- job:
+    name: requirements-check-self
+    description: |
+      Run the requirements-check job on another repo in order to
+      self-test changes to its job configuration.
+    parent: requirements-check
+    # This could be any project, nova is chosen arbitrarily.
+    required-projects: openstack/nova
+    vars:
+      zuul_work_dir: "{{ zuul.projects['opendev.org/openstack/nova'].src_dir }}"
+      zuul_branch: "master"

.zuul.d/project.yaml

@@ -13,6 +13,7 @@
             files:
               - bindep.txt
         - openstack-tox-validate
+        - requirements-check-self
         - requirements-tox-babel
         - requirements-tox-bindep:
             voting: false
@@ -79,6 +80,7 @@
             files:
               - bindep.txt
         - openstack-tox-validate
+        - requirements-check-self
         - requirements-tox-babel
         - requirements-tox-py39-check-uc
         - requirements-tox-py310-check-uc

playbooks/requirements-check.yaml

@@ -1,16 +1,4 @@
 - hosts: all
-  pre_tasks:
-    - name: Ensure pip
-      include_role:
-        name: ensure-pip
-
-  tasks:
-    - name: Install openstack_requirements
-      command: "pip3 install --user {{ zuul.projects['opendev.org/openstack/requirements'].src_dir }}"
-
-    - name: Run requirements check script
-      # Use command module here instead of script since Zuul gets output
-      # with command into job-output.txt file.
-      # Command expects the file to be at the remote system - the system
-      # running the tests. Ask zuul variables for the path.
-      command: "{{ zuul.projects['opendev.org/openstack/requirements'].src_dir }}/playbooks/files/project-requirements-change.py {{ zuul.project.src_dir }} {{ zuul.branch }}"
+  roles:
+    - ensure-pip
+    - check-requirements

roles/check-requirements/README.rst

@@ -0,0 +1,13 @@
+Check that a project's requirements match the global requirements repo.
+
+**Role Variables**
+
+.. zuul:rolevar:: zuul_work_dir
+   :default: {{ zuul.project.src_dir }}
+
+   Directory holding the project to check.
+
+.. zuul:rolevar:: zuul_branch
+   :default: {{ zuul.branch }}
+
+   Branch to check.

roles/check-requirements/defaults/main.yaml

@@ -0,0 +1,2 @@
+zuul_work_dir: "{{ zuul.project.src_dir }}"
+zuul_branch: "{{ zuul.branch }}"

roles/check-requirements/tasks/main.yaml

@@ -0,0 +1,9 @@
+- name: Install openstack_requirements
+  command: "pip3 install --user {{ zuul.projects['opendev.org/openstack/requirements'].src_dir }}"
+
+- name: Run requirements check script
+  # Use command module here instead of script since Zuul gets output
+  # with command into job-output.txt file.
+  # Command expects the file to be at the remote system - the system
+  # running the tests. Ask zuul variables for the path.
+  command: "{{ zuul.projects['opendev.org/openstack/requirements'].src_dir }}/playbooks/files/project-requirements-change.py {{ zuul_work_dir }} {{ zuul_branch }}"