Release CI: extract the newest bit of CHANGELOG as release text

Author: wilfwilson

.github/workflows/release.yml

@@ -9,6 +9,11 @@ on:
         type: boolean
         required: false
         default: false
+      force:
+        description: "Allow overwriting an existing release, or making a release with an incorrect date"
+        type: boolean
+        required: false
+        default: false
 
 permissions: write-all
 
@@ -30,9 +35,40 @@ jobs:
         run: |
           rm -f  .covignore .mailmap .codespellrc Dockerfile
           rm -rf etc scripts
-      - uses: gap-actions/release-pkg@v1
+      - name: Extract the latest CHANGELOG entry to use as the GitHub release text
+        run: |
+          # Extract the part of CHANGELOG that is relevant to this release
+          LINES=`grep -n "## Version " CHANGELOG.md | head -2 | cut -d':' -f1`
+
+          # Find the line number where the relevant section starts
+          # (Increment by 1 if that first line is empty)
+          START=`echo $LINES | cut -d' ' -f1`;
+          START=$((START + 1))
+          if [ "`sed \"${START}q;d\" CHANGELOG.md`" == "" ]; then
+            START=$(( START + 1 ));
+          fi
+
+          # Find the line number where the relevant section ends
+          # (Decrement by 1 if that last line is empty)
+          STOP=`echo $LINES | cut -d' ' -f2`;
+          STOP=$((STOP - 1))
+          if [ "`sed \"${STOP}q;d\" CHANGELOG.md`" == "" ]; then
+            STOP=$(( STOP - 1 ));
+          fi
+
+          # Store the potentially multi-line text in the BODY environment so
+          # that we can pass it to the release-pkg action as an input
+          {
+            echo 'BODY<<EOF'
+            sed -n "${START},${STOP}p" CHANGELOG.md
+            echo EOF
+          } >> "$GITHUB_ENV"
+
+      - uses: wilfwilson/release-pkg@add-body-text-option
         with:
           dry-run: ${{ inputs.dry-run }}
+          force: ${{ inputs.force }}
+          body-text: ${{ env.BODY }}
       - uses: gap-actions/update-gh-pages@v1
         if: ${{ !inputs.dry-run }}
         with: