CI: Force changelog updates

Changelog updates are now required in MRs by default. If there is a
match for "\<skip.\?changelog\>" in the commit message, this will be
ignored.

$CI_COMMIT_MESSAGE mangles newlines so it's not possible to require the
string to be on its own line, that means it would also trigger within a
wall of text, which makes it less obvious.

Also, I wasn't able to find a CI variable which has the ref of the
branch the MR is set against, to build a tree-ish than spans over the
whole MR and not just HEAD.

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

.gitlab-ci.yml

@@ -68,6 +68,26 @@ rustfmt:
     - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
     - if: $CI_PIPELINE_SOURCE == 'push' && $CI_COMMIT_REF_NAME == 'main'
 
+changelog-update:
+  stage: lint
+  image: alpine:latest
+  # Check in the commit message for "skip.?changelog", if not present
+  # then check for changes in changelogs.
+  # XXX: It looks like $CI_COMMIT_MESSAGE mangles newlines so it's not
+  # possible to require the "skip.?changelog" string to be on its own line,
+  # that means it would also trigger within a wall of text. Not so obvious.
+  # TODO: Check the whole MR for updates in changelogs, not just the last
+  # commit.
+  script:
+    - apk add --no-cache python3 git
+    - python3 --version
+    - git version
+    - git log --oneline "${CI_MERGE_REQUEST_DIFF_BASE_SHA}.." --
+    - python3 .forgejo/workflows/check-changelog.py
+  rules:
+    - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
+    - if: $CI_PIPELINE_SOURCE == 'push' && $CI_COMMIT_REF_NAME == 'main'
+
 stable-test:
   extends:
     - .test