gitlab-ci.yml: Avoid running CI for merge pipelines

This avoids running pipelines *after* the MR has been merged and
avoids triggering a new CI build and with it the tests.

These should already be done in the MR context so there's no need to
run them once more time.

Further more, with this change forks would need to manually trigger
builds. No change for the MR context, as these it would build automatically.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

.gitlab-ci.yml

@@ -58,11 +58,25 @@ include:
     ref: *template_sha
     file: '/templates/ci-fairy.yml'
 
+.default-rules:
+  rules:
+    # do not duplicate pipelines on merge pipelines
+    - if: $CI_COMMIT_BRANCH && $CI_OPEN_MERGE_REQUESTS && $CI_PIPELINE_SOURCE == "push"
+      when: never
+    # we need a default case though, so all the rest still run
+    - when: on_success
+
+.merge-rules:
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+      when: always
+    - when: never
 
 # Define the build stages. These are used for UI grouping as well as
 # dependencies.
 stages:
   - "Merge request checks"
+  - "Pre Base container"
   - "Base container"
   - "Full build and test"
   - "No-GL build and test"
@@ -86,19 +100,12 @@ stages:
     FDO_DISTRIBUTION_VERSION: bookworm
     FDO_DISTRIBUTION_EXEC: 'env FDO_CI_CONCURRENT=${FDO_CI_CONCURRENT} BUILD_ARCH=${BUILD_ARCH} KERNEL_IMAGE=${KERNEL_IMAGE} KERNEL_DEFCONFIG=${KERNEL_DEFCONFIG} LLVM_VERSION=${LLVM_VERSION} FDO_DISTRIBUTION_VERSION=${FDO_DISTRIBUTION_VERSION} bash .gitlab-ci/debian-install.sh'
 
-.ci-rules:
-  rules:
-    - when: on_success
-
-# Does not inherit .ci-rules as we only want it to run in MR context.
+# Does not inherit .default-rules as we only want it to run in MR context.
 check-commit:
   extends:
     - .fdo.ci-fairy
+    - .merge-rules
   stage: "Merge request checks"
-  rules:
-    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
-      when: always
-    - when: never
   script:
     - ci-fairy check-commits --signed-off-by --junit-xml=results.xml
     - ci-fairy check-merge-request --require-allow-collaboration --junit-xml=results.xml
@@ -154,66 +161,87 @@ check-commit:
     KERNEL_DEFCONFIG: "defconfig"
     QEMU_SMP: 8 # built-in QEmu limit
 
+base-container-pre:
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+      when: always
+    # default, only run by default on MR.
+    - when: manual
+  stage: "Pre Base container"
+  script: echo "exit 0"
+
 # Build our base container image, which contains the core distribution, the
 # toolchain, and all our build dependencies. This will be reused in the build
 # stage.
 x86_64-debian-lts-container_prep:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-lts-x86_64
     - .fdo.container-build@debian
   timeout: 30m
+  needs:
+    - job: base-container-pre
   stage: "Base container"
 
 x86_64-debian-container_prep:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-x86_64
     - .fdo.container-build@debian
+  needs:
+    - job: base-container-pre
   timeout: 30m
   stage: "Base container"
 
 armv7-debian-lts-container_prep:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-lts-armv7
     - .fdo.container-build@debian
   tags:
     - aarch64
   variables:
     FDO_BASE_IMAGE: "arm32v7/debian:$FDO_DISTRIBUTION_VERSION"
+  needs:
+    - job: base-container-pre
   timeout: 30m
   stage: "Base container"
 
 armv7-debian-container_prep:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-armv7
     - .fdo.container-build@debian
   tags:
     - aarch64
   variables:
     FDO_BASE_IMAGE: "arm32v7/debian:$FDO_DISTRIBUTION_VERSION"
+  needs:
+    - job: base-container-pre
   timeout: 30m
   stage: "Base container"
 
 aarch64-debian-lts-container_prep:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-lts-aarch64
     - .fdo.container-build@debian
   tags:
     - aarch64
+  needs:
+    - job: base-container-pre
   timeout: 30m
   stage: "Base container"
 
 aarch64-debian-container_prep:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-aarch64
     - .fdo.container-build@debian
   tags:
     - aarch64
+  needs:
+    - job: base-container-pre
   timeout: 30m
   stage: "Base container"
 
@@ -241,7 +269,7 @@ aarch64-debian-container_prep:
 # backend using the 'vkms' virtual driver under Linux.
 .build-and-test:
   extends:
-  - .ci-rules
+  - .default-rules
   script:
   - cd "$BUILDDIR"
   - meson --prefix="$PREFIX" --wrap-mode=nofallback -Db_sanitize=address ${MESON_OPTIONS} ${MESON_TOOLCHAIN_OPTIONS} ..
@@ -269,7 +297,7 @@ aarch64-debian-container_prep:
 # Same as above, but without running any tests.
 .build-no-test:
   extends:
-  - .ci-rules
+  - .default-rules
   script:
   - cd "$BUILDDIR"
   - meson --prefix="$PREFIX" --wrap-mode=nofallback ${MESON_OPTIONS} ..
@@ -528,7 +556,7 @@ aarch64-debian-no-gl-build:
 # invariant across any architecture or OS.
 docs-and-coverage:
   extends:
-    - .ci-rules
+    - .default-rules
     - .debian-x86_64
     - .fdo.suffixed-image@debian
   stage: pages
@@ -554,7 +582,7 @@ docs-and-coverage:
 # Generate the documentation for https://wayland.pages.freedesktop.org/weston/
 # Anything under public/ is published to this URL.
 #
-# Does not inherit .ci-rules as it should only run in our default branch for
+# Does not inherit .default-rules as it should only run in our default branch for
 # the upstream repo.
 pages:
   extends: