tools/changelog-helper: Ignore foreign-milestone PRs despite mentions…

… in git log

Previously, all PRs from the relevant git log were added to the
ChangeLog. This causes false positives when older PRs are intentionally
mentioned again (e.g. for further fixes or documentation updates).
At the same time, simply skipping them removes an additional method to
avoid forgotten PRs.

Therefore, only add git-mentioned PRs if they don't have a milestone (or
a matching one).

Fixes: jamulussoftware#2657

tools/changelog-helper.sh

@@ -44,9 +44,15 @@ find_or_add_missing_entries() {
         target_ref="${target_release_tag}"
     fi
     echo
-    echo "Checking if all PR or references in git log since ${prev_release_tag} are included for ${target_release} based on ref ${target_ref}..."
+    echo "Checking if all PR references in git log since ${prev_release_tag} are included for ${target_release} based on ref ${target_ref}..."
+    local milestone
     for id in $(git log "${prev_release_tag}..master" | grep -oP '#\K(\d+)'); do
         gh pr view "${id}" --json title &> /dev/null || continue # Skip non-PRs
+        milestone=$(gh pr view "${id}" --json milestone --jq .milestone.title)
+        if [[ "${milestone}" =~ "Release " ]] && [[ "${milestone}" != "Release ${target_release}" ]]; then
+            echo "-> Ignoring PR #${id}, which was mentioned in 'git log ${prev_release_tag}..HEAD', but already has milestone '${milestone}'"
+            continue
+        fi
         check_or_add_pr "${id}"
     done