[RFC PATCH v2 09/11] gitlab-ci: Add rules to select cross-jobs to build

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Add rules to select some crossbuild jobs.

The following tags are available to restrict the CI jobs:
- all    (select all jobs, this is default)
- cross  (select all cross-jobs)
- system (select all cross-system jobs)
- user   (select all cross-user jobs)
- $ARCH  (select an architecture: arm/mips/ppc/sparc/...)

Developers can combine tags in the QEMU_BUILD variable when
pushing a branch (or tag) to repositories. Examples:

  $ git push -o ci.variable="QEMU_BUILD=user"        myrepo mybranch
  $ git push -o ci.variable="QEMU_BUILD=user,system" myrepo mybranch

References:
- https://docs.gitlab.com/ee/ci/yaml/#rulesif
- https://docs.gitlab.com/ee/user/project/push_options.html#push-options-for-gitlab-cicd

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 .gitlab-ci.d/crossbuilds.yml | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/.gitlab-ci.d/crossbuilds.yml b/.gitlab-ci.d/crossbuilds.yml
index 701550f028c..7503d24a57b 100644
--- a/.gitlab-ci.d/crossbuilds.yml
+++ b/.gitlab-ci.d/crossbuilds.yml
@@ -1,6 +1,36 @@
 .cross_common_job:
   stage: build
   image: $CI_REGISTRY_IMAGE/qemu/$IMAGE:latest
+  rules:
+    # If the if statement is true, the job is added to the pipeline.
+    # We only filter for push events
+    - if: '$CI_PIPELINE_SOURCE != "push"'
+    # Build all when no variable defined, or set to "all"
+    - if: $QEMU_BUILD == null || $QEMU_BUILD =~ /^all$/
+    # Build specific job name
+    - if: $QEMU_BUILD =~ /^$CI_JOB_NAME$/
+    # Build set of jobs by feature
+    - if: $QEMU_BUILD =~ /cross/
+    - if: $QEMU_BUILD =~ /system/ && $CI_JOB_NAME =~ /system/
+    - if: $QEMU_BUILD =~ /user/ && $CI_JOB_NAME =~ /user/
+    # Build set of jobs by arch
+    - if: $QEMU_BUILD =~ /aarch64/ && ($CI_JOB_NAME =~ /aarch64/ || $IMAGE =~ /aarch64/)
+    - if: $QEMU_BUILD =~ /alpha/ && ($CI_JOB_NAME =~ /alpha/ || $IMAGE =~ /alpha/)
+    - if: $QEMU_BUILD =~ /arm/ && ($CI_JOB_NAME =~ /arm/ || $IMAGE =~ /arm/)
+    - if: $QEMU_BUILD =~ /avr/ && ($CI_JOB_NAME =~ /avr/ || $IMAGE =~ /avr/)
+    - if: $QEMU_BUILD =~ /hppa/ && ($CI_JOB_NAME =~ /hppa/ || $IMAGE =~ /hppa/)
+    - if: $QEMU_BUILD =~ /i386/ && ($CI_JOB_NAME =~ /i386/ || $IMAGE =~ /i386/)
+    - if: $QEMU_BUILD =~ /lm32/ && ($CI_JOB_NAME =~ /lm32/ || $IMAGE =~ /lm32/)
+    - if: $QEMU_BUILD =~ /m68k/ && ($CI_JOB_NAME =~ /m68k/ || $IMAGE =~ /m68k/)
+    - if: $QEMU_BUILD =~ /ppc/ && ($CI_JOB_NAME =~ /ppc/ || $IMAGE =~ /ppc/)
+    - if: $QEMU_BUILD =~ /riscv/ && ($CI_JOB_NAME =~ /riscv/ || $IMAGE =~ /riscv/)
+    - if: $QEMU_BUILD =~ /s390x/ && ($CI_JOB_NAME =~ /s390x/ || $IMAGE =~ /s390x/)
+    - if: $QEMU_BUILD =~ /sparc/ && ($CI_JOB_NAME =~ /sparc/ || $IMAGE =~ /sparc/)
+    - if: $QEMU_BUILD =~ /tricore/ && ($CI_JOB_NAME =~ /tricore/ || $IMAGE =~ /tricore/)
+    - if: $QEMU_BUILD =~ /x86/ && ($CI_JOB_NAME =~ /x86/ || $IMAGE =~ /x86/)
+    - if: $QEMU_BUILD =~ /xtensa/ && ($CI_JOB_NAME =~ /xtensa/ || $IMAGE =~ /xtensa/)
+    # In all other cases, the job is excluded from a pipeline.
+    - when: never
 
 .cross_system_build_job:
   extends: .cross_common_job
-- 
2.26.2