gitlab: introduce a common base job template

Currently job rules are spread across the various templates
and jobs, making it hard to understand exactly what runs in
what scenario. This leads to inconsistency in the rules and
increased maint burden.

The intent is that we introduce a common '.base_job_template'
which will have a general purpose 'rules:' block. No other
template or job should define 'rules:', but instead they must
rely on the inherited rules. To allow behaviour to be tweaked,
rules will be influenced by a number of variables with the
naming scheme 'QEMU_JOB_nnnn'.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220526110705.59952-2-berrange@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220527153603.887929-29-alex.bennee@linaro.org>

.gitlab-ci.d/base.yml

@@ -0,0 +1,28 @@
+
+# The order of rules defined here is critically important.
+# They are evaluated in order and first match wins.
+#
+# Thus we group them into a number of stages, ordered from
+# most restrictive to least restrictive
+#
+.base_job_template:
+  rules:
+    #############################################################
+    # Stage 1: exclude scenarios where we definitely don't
+    # want jobs to run
+    #############################################################
+
+
+    #############################################################
+    # Stage 2: fine tune execution of jobs in specific scenarios
+    # where the catch all logic is inapprorpaite
+    #############################################################
+
+
+    #############################################################
+    # Stage 3: catch all logic applying to any job not matching
+    # an earlier criteria
+    #############################################################
+
+    # Jobs can run if any jobs they depend on were successfull
+    - when: on_success

.gitlab-ci.d/qemu-project.yml

@@ -2,6 +2,7 @@
 # https://gitlab.com/qemu-project/qemu/-/pipelines
 
 include:
+  - local: '/.gitlab-ci.d/base.yml'
   - local: '/.gitlab-ci.d/stages.yml'
   - local: '/.gitlab-ci.d/edk2.yml'
   - local: '/.gitlab-ci.d/opensbi.yml'

docs/devel/ci-jobs.rst.inc

@@ -28,7 +28,35 @@ For further information about how to set these variables, please refer to::
 
   https://docs.gitlab.com/ee/user/project/push_options.html#push-options-for-gitlab-cicd
 
-Here is a list of the most used variables:
+Variable naming and grouping
+----------------------------
+
+The variables used by QEMU's CI configuration are grouped together
+in a handful of namespaces
+
+ * QEMU_JOB_nnnn - variables to be defined in individual jobs
+   or templates, to influence the shared rules defined in the
+   .base_job_template.
+
+ * QEMU_CI_nnn - variables to be set by contributors in their
+   repository CI settings, or as git push variables, to influence
+   which jobs get run in a pipeline
+
+ * nnn - other misc variables not falling into the above
+   categories, or using different names for historical reasons
+   and not yet converted.
+
+Maintainer controlled job variables
+-----------------------------------
+
+The following variables may be set when defining a job in the
+CI configuration file.
+
+Contributor controlled runtime variables
+----------------------------------------
+
+The following variables may be set by contributors to control
+job execution
 
 QEMU_CI_AVOCADO_TESTING
 ~~~~~~~~~~~~~~~~~~~~~~~
@@ -38,6 +66,12 @@ these artifacts are not already cached, downloading them make the jobs
 reach the timeout limit). Set this variable to have the tests using the
 Avocado framework run automatically.
 
+Other misc variables
+--------------------
+
+These variables are primarily to control execution of jobs on
+private runners
+
 AARCH64_RUNNER_AVAILABLE
 ~~~~~~~~~~~~~~~~~~~~~~~~
 If you've got access to an aarch64 host that can be used as a gitlab-CI