add script to extract release notes from change log

.gitlab-ci.yml

@@ -141,8 +141,7 @@ release:
     - upload
   script:
     - echo "Creating GitLab Release for ${CI_COMMIT_TAG}"
-    - PREV_TAG=$(git describe --tags --abbrev=0 $(git rev-list --tags --skip=1 --max-count=1) 2>/dev/null || echo "")
-    - if [ -n "$PREV_TAG" ]; then git log --pretty=format:"- [%h](https://gitlab.com/${CI_PROJECT_PATH}/-/commit/%H) %s" ${PREV_TAG}..${CI_COMMIT_TAG} --no-merges > release_notes.md; else echo "Initial release" > release_notes.md; fi
+    - sh ./build-aux/extract-changelog-for-tag.sh ./CHANGELOG.md ${CI_COMMIT_TAG} > release_notes.md
   release:
     name: "Release ${CI_COMMIT_TAG}"
     description: "$(cat release_notes.md)"

build-aux/extract-changelog-for-tag.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+if [ "$#" -ne 2 ]; then
+  echo "Usage: $0 <changelog file> <tag>"
+  exit 1
+fi
+
+CHANGELOG_FILE=$1
+CURRENT_TAG=$2
+PREVIOUS_TAG=$(git describe --tags --abbrev=0 "${CURRENT_TAG}"^)
+
+# Extract content between the two tags
+awk "/^## \[${CURRENT_TAG}\] - / {flag=1; next} /^## \[${PREVIOUS_TAG}\] - / {flag=0; exit} flag" "${CHANGELOG_FILE}" |
+  # Remove leading and trailing empty lines
+  sed -e '1{/^$/d;}' -e '${/^$/d;}'