Remove all leading and trailing newlines from generated release notes

Author: ruohola

.github/workflows/cd.yml

@@ -27,8 +27,9 @@ jobs:
         run: sed -i 's/^version *=.*/version = "${{ github.event.inputs.version }}"/' pyproject.toml
 
       - name: "Extract version's changelog for release notes and tag message"
-        # Find the lines between the first `## [<number>` and the second `## [<number>`.
-        run: sed '1,/^## *\[[0-9]/d;/^## *\[[0-9]/Q' CHANGELOG.md > release_notes.txt
+        # 1. Find the lines between the first `## [<number>` and the second `## [<number>`.
+        # 2. Remove all leading and trailing newlines from the output.
+        run: sed '1,/^## *\[[0-9]/d;/^## *\[[0-9]/Q' CHANGELOG.md | sed -e :a -e '/./,$!d;/^\n*$/{$d;N;};/\n$/ba' > release_notes.txt
 
       - name: "Set up Python"
         id: setup-python