[devscripts] Allow using OCP stable versions

With this patch, ci-fmw allows to configure devscripts openshift_version
values "stable-<majorversion>" (e.g. "stable-4.18") which is dynamically
updated every time a new minor version becomes the latest stable.

Example:
https://mirror.openshift.com/pub/openshift-v4/clients/ocp/stable-4.18/

Author: eduolivares

roles/devscripts/README.md

@@ -76,6 +76,11 @@ If you provide neither, or both, it will fail.
 
 ### Supported keys in cifmw_devscripts_config_overrides
 
+The `openshift_version` value can be set to either a minor version "X.Y.Z" (e.g.
+4.16.0) or a stable version "stable-X.Y" (e.g. stable-4.16), which would be
+translated to the corresponding minor version.
+Allowed values can be found [here](https://mirror.openshift.com/pub/openshift-v4/clients/ocp/)
+
 | Key | Default Value | Description |
 | --- | ------------- | ----------- |
 | working_dir | `/home/dev-scripts` | Path to the directory to store script artifacts. |

roles/devscripts/tasks/build_config.yml

@@ -40,6 +40,16 @@
       devscripts_config_patches
     }}
 
+- name: Replace OCP version if "stable-" alias used
+  when:
+    - cifmw_devscripts_config.openshift_version.startswith("stable-")
+  vars:
+    _ocp_release_txt: "{{ lookup('ansible.builtin.url', 'https://mirror.openshift.com/pub/openshift-v4/clients/ocp/' ~ cifmw_devscripts_config.openshift_version ~ '/release.txt', split_lines=False) }}"
+    _ocp_release_name: "{{ _ocp_release_txt | regex_search('^Name:.*', multiline=True) }}"
+    _ocp_release_version: "{{ _ocp_release_name.split()[1] }}"
+  ansible.builtin.set_fact:
+    cifmw_devscripts_config: "{{ cifmw_devscripts_config | combine({'openshift_version': _ocp_release_version}) }}"
+
 - name: Ensure output directory exists
   become: true
   ansible.builtin.file: