Only run relevant CI jobs based on the changes

Trigger selected CI jobs on MR automatically only if there are related
code changes. Otherwise, offer an option to run the jobs manually in
MRs. For other sources, like schedules, tags etc., execute the jobs as
usual.

.gitlab-ci.yml

@@ -273,19 +273,73 @@ stages:
 
 ### Job Templates
 
+.rule_mr_code: &rule_mr_code
+  - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+    changes:
+      - '**/*.c'
+      - '**/*.h'
+      - '**/meson.build'
+
+.rule_mr_shell: &rule_mr_shell
+  - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+    changes:
+      - '**/*.sh'
+      - '**/*.sh.in'
+      - 'bin/tests/system/org.isc.bind.system'
+
+.rule_mr_python: &rule_mr_python
+  - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+    changes:
+      - '**/*.py'
+
+.rule_mr_manual: &rule_mr_manual
+  - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+    when: manual  # only run on MR if requested
+    allow_failure: true  # don't block the pipeline or the pipeline result
+
+.rule_tag: &rule_tag
+  - if: '$CI_COMMIT_TAG != null'
+
+.rule_source_other_than_mr: &rule_source_other_than_mr
+  - if: '$CI_PIPELINE_SOURCE =~ /^(api|pipeline|schedule|trigger|web)$/'
+
+.rule_source_all: &rule_source_all
+  - if: '$CI_PIPELINE_SOURCE =~ /^(api|merge_request_event|pipeline|schedule|trigger|web)$/'
+
 .api-pipelines-schedules-tags-triggers-web-triggering-rules: &api_pipelines_schedules_tags_triggers_web_triggering_rules
   rules:
-    - if: '$CI_PIPELINE_SOURCE =~ /^(api|pipeline|schedule|trigger|web)$/'
-    - if: '$CI_COMMIT_TAG != null'
+    - *rule_tag
+    - *rule_source_other_than_mr
 
 .default-triggering-rules_list: &default_triggering_rules_list
-  - if: '$CI_PIPELINE_SOURCE =~ /^(api|merge_request_event|pipeline|schedule|trigger|web)$/'
-  - if: '$CI_COMMIT_TAG != null'
+  - *rule_tag
+  - *rule_source_all
 
 .default-triggering-rules: &default_triggering_rules
   rules:
     - *default_triggering_rules_list
 
+.code-triggering-rules: &code_triggering_rules
+  rules:
+    - *rule_mr_code
+    - *rule_mr_manual
+    - *rule_tag
+    - *rule_source_other_than_mr
+
+.shell-triggering-rules: &shell_triggering_rules
+  rules:
+    - *rule_mr_shell
+    - *rule_mr_manual
+    - *rule_tag
+    - *rule_source_other_than_mr
+
+.python-triggering-rules: &python_triggering_rules
+  rules:
+    - *rule_mr_python
+    - *rule_mr_manual
+    - *rule_tag
+    - *rule_source_other_than_mr
+
 .precheck: &precheck_job
   <<: *default_triggering_rules
   <<: *base_image
@@ -400,8 +454,17 @@ stages:
   stage: performance
   rules:
     - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      changes:
+        - '**/*.c'
+        - '**/*.h'
       variables:
         BASELINE: '$CI_MERGE_REQUEST_DIFF_BASE_SHA'
+    - &shotgun_rule_mr_manual
+      if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      variables:
+        BASELINE: '$CI_MERGE_REQUEST_DIFF_BASE_SHA'
+      when: manual  # don't run on each MR unless requested
+      allow_failure: true
     - &shotgun_rule_tag
       if: '$CI_COMMIT_TAG != null'
       variables:
@@ -521,6 +584,7 @@ stages:
     - find build/man/ -maxdepth 2 -name "*.[0-9]" -exec mandoc -T lint "{}" \; | ( ! grep -v -e "skipping paragraph macro. sp after" -e "unknown font, skipping request. ft C" -e "input text line longer than 80 bytes" )
 
 .respdiff: &respdiff_job
+  <<: *code_triggering_rules
   stage: system
   before_script:
     - *configure
@@ -561,6 +625,7 @@ misc:
 
 black:
   <<: *precheck_job
+  <<: *python_triggering_rules
   needs: []
   script:
     - black $(git ls-files '*.py')
@@ -574,6 +639,7 @@ black:
 
 vulture:
   <<: *precheck_job
+  <<: *python_triggering_rules
   needs: []
   script:
     - vulture --exclude "*ans.py,conftest.py,isctest" --ignore-names "pytestmark,reconfigure_policy,setup_filters" bin/tests/system/
@@ -603,6 +669,16 @@ ci-orphaned-anchors:
 
 clang-format:
   <<: *precheck_job
+  rules:
+    - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      changes:
+        - '**/*.c'
+        - '**/*.h'
+        - '**/.clang-format'
+        - '**/.clang-format.headers'
+    - *rule_mr_manual
+    - *rule_tag
+    - *rule_source_other_than_mr
   needs: []
   script:
     - if [ -r .clang-format ]; then "${CLANG_FORMAT}" -i -style=file $(git ls-files '*.c' '*.h'); fi
@@ -616,6 +692,15 @@ clang-format:
 
 coccinelle:
   <<: *precheck_job
+  rules:
+    - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      changes:
+        - '**/*.c'
+        - '**/*.h'
+        - 'cocci/**'
+    - *rule_mr_manual
+    - *rule_tag
+    - *rule_source_other_than_mr
   needs: []
   script:
     - util/check-cocci.sh
@@ -623,6 +708,13 @@ coccinelle:
 
 meson-format:
   <<: *precheck_job
+  rules:
+    - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      changes:
+        - '**/meson.build'
+    - *rule_mr_manual
+    - *rule_tag
+    - *rule_source_other_than_mr
   needs: []
   script:
     - git ls-files "*meson.build" | xargs muon-meson fmt -i
@@ -651,6 +743,7 @@ doctest:
 
 pylint:
   <<: *precheck_job
+  <<: *python_triggering_rules
   needs: []
   variables:
     PYTHONPATH: "${CI_PROJECT_DIR}/bin/tests/system"
@@ -670,6 +763,7 @@ reuse:
 
 shfmt:
   <<: *precheck_job
+  <<: *shell_triggering_rules
   needs: []
   script:
     - shfmt -w -i 2 -ci -bn . $(find . -name "*.sh.in")
@@ -692,12 +786,14 @@ danger:
 
 checkbashisms:
   <<: *precheck_job
+  <<: *shell_triggering_rules
   needs: []
   script:
     - checkbashisms $(find . -path './.git' -prune -o -type f -exec sh -c 'head -n 1 "{}" | grep -qsF "#!/bin/sh"' \; -print)
 
 mypy:
   <<: *precheck_job
+  <<: *python_triggering_rules
   stage: precheck
   script:
     - mypy "bin/tests/system/isctest/"
@@ -1677,7 +1773,6 @@ coverity:
 
 respdiff:
   <<: *respdiff_job
-  <<: *default_triggering_rules
   <<: *base_image
   variables:
     CC: gcc
@@ -1690,7 +1785,6 @@ respdiff:
 
 respdiff:asan:
   <<: *respdiff_job
-  <<: *default_triggering_rules
   <<: *base_image
   variables:
     CC: gcc
@@ -1703,7 +1797,6 @@ respdiff:asan:
 
 respdiff:tsan:
   <<: *respdiff_job
-  <<: *default_triggering_rules
   <<: *tsan_debian_trixie_amd64_image
   variables:
     CC: "${CLANG}"
@@ -1720,7 +1813,6 @@ respdiff:tsan:
 
 respdiff-third-party:
   <<: *respdiff_job
-  <<: *default_triggering_rules
   <<: *base_image
   variables:
     CC: gcc
@@ -1734,7 +1826,6 @@ respdiff-third-party:
 .respdiff-recent-named: &respdiff_recent_named
   <<: *respdiff_job
   <<: *base_image
-  <<: *default_triggering_rules
   needs:
     - job: ci-variables
       artifacts: true
@@ -1777,12 +1868,8 @@ shotgun:dot:
   variables:
     SHOTGUN_SCENARIO: dot
     SHOTGUN_TRAFFIC_MULTIPLIER: 5
-  rules: &shotgun_rules_manual_mr
-    - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
-      variables:
-        BASELINE: '$CI_MERGE_REQUEST_DIFF_BASE_SHA'
-      when: manual  # don't run on each MR unless requested
-      allow_failure: true
+  rules:
+    - *shotgun_rule_mr_manual
     - *shotgun_rule_tag
     - *shotgun_rule_other
 
@@ -1792,7 +1879,10 @@ shotgun:doh-get:
     SHOTGUN_SCENARIO: doh-get
     SHOTGUN_TRAFFIC_MULTIPLIER: 2
     SHOTGUN_EVAL_THRESHOLD_LATENCY_PCTL_MAX: 0.4  # bump from the default due to increased tail-end jitter
-  rules: *shotgun_rules_manual_mr
+  rules:
+    - *shotgun_rule_mr_manual
+    - *shotgun_rule_tag
+    - *shotgun_rule_other
 
 generate-stress-test-configs:
   <<: *base_image
@@ -1809,6 +1899,16 @@ generate-stress-test-configs:
 stress-test-child-pipeline:
   <<: *default_triggering_rules
   stage: performance
+  rules:
+    - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      changes:
+        - '**/*.c'
+        - '**/*.h'
+    - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
+      when: manual  # don't run on each MR unless requested
+      allow_failure: true
+    - if: '$CI_COMMIT_TAG != null'
+    - if: '$CI_PIPELINE_SOURCE =~ /^(api|pipeline|schedule|trigger|web)$/'
   trigger:
     include:
       - artifact: stress-test-configs.yml