Fix duplicate changelog entry in post-release PR (#480)

Author: trask

.github/scripts/merge-change-log-after-release.sh

@@ -4,41 +4,29 @@
 # the release date for $VERSION should be available in $RELEASE_DATE
 # and the release notes for $VERSION should be available in /tmp/changelog-section.md
 
-if [[ $VERSION =~ ^[0-9]+\.[0-9]+\.0 ]]; then
-  # this was not a patch release, so the version exists already in the CHANGELOG.md
-
-  # update the release date
-  sed -Ei "s/## Version $VERSION .*/## Version $VERSION ($RELEASE_DATE)/" CHANGELOG.md
-
-  # the entries are copied over from the release branch to support workflows
-  # where change log entries may be updated after preparing the release branch
-
-  {
-    # copy the portion above the release, up to and including the heading
-    sed -n "0,/^## Version $VERSION /p" CHANGELOG.md
-    # copy the release notes for $VERSION
-    cat /tmp/changelog-section.md
-    # copy the portion below the release
-    sed -n "0,/^## Version $VERSION /d;0,/^## Version /{/^## Version/!d};p" CHANGELOG.md
-  } > /tmp/CHANGELOG.md
-
-  # update the real CHANGELOG.md
-  cp /tmp/CHANGELOG.md CHANGELOG.md
-
-else
-  # this was a patch release, so the version does not exist already in the CHANGELOG.md
-
-  {
-    # copy the portion above the top-most release, not including the heading
-    sed -n "0,/^## Version /{ /^## Version /!p }" CHANGELOG.md
-    # add the heading
-    echo "## Version $VERSION ($RELEASE_DATE)"
-    # copy the release notes for $VERSION
-    cat /tmp/changelog-section.md
-    # copy the portion starting from the top-most release
-    sed -n "/^## Version /,\$p" CHANGELOG.md
-  } > /tmp/CHANGELOG.md
-
-  # update the real CHANGELOG.md
-  cp /tmp/CHANGELOG.md CHANGELOG.md
-fi
+# NOTE: this script differs from the equivalent in other Java repos (where it
+# was copied from). In those repos patch releases are cut from the prior
+# minor's release branch, so the patch version heading is not yet present in
+# CHANGELOG.md on main and must be prepended here. In this repo, patch
+# releases also go through the prepare-release-branch workflow, which already
+# adds the heading to main, so we always take the "heading already exists"
+# path below (both for minor and patch releases). Please preserve this
+# difference when syncing workflow changes from other Java repos.
+
+# update the release date
+sed -Ei "s/## Version $VERSION .*/## Version $VERSION ($RELEASE_DATE)/" CHANGELOG.md
+
+# the entries are copied over from the release branch to support workflows
+# where change log entries may be updated after preparing the release branch
+
+{
+  # copy the portion above the release, up to and including the heading
+  sed -n "0,/^## Version $VERSION /p" CHANGELOG.md
+  # copy the release notes for $VERSION
+  cat /tmp/changelog-section.md
+  # copy the portion below the release
+  sed -n "0,/^## Version $VERSION /d;0,/^## Version /{/^## Version/!d};p" CHANGELOG.md
+} > /tmp/CHANGELOG.md
+
+# update the real CHANGELOG.md
+cp /tmp/CHANGELOG.md CHANGELOG.md