chore: deduplicate the release changelog automatically

.github/workflows/release-please.yml

@@ -59,3 +59,55 @@ jobs:
             --repo-url "$GITHUB_REPOSITORY" \
             --config-file release-please-config.json \
             --manifest-file .release-please-manifest.json
+
+      # release-please lists the same change twice whenever a pull request was
+      # merged with a GitHub merge commit. The merge commit carries the pull
+      # request title in its body:
+      #
+      #   Merge pull request #171 from strapi-community/feat/cache-dashboard
+      #
+      #   feat: add a cache statistics endpoint for the admin dashboard
+      #
+      # and release-please parses every conventional commit it finds in a
+      # message, so that body line becomes an entry attributed to the merge
+      # commit, while the commit on the branch underneath produces an identical
+      # one. There is no setting for it: BEGIN_COMMIT_OVERRIDE is keyed on the
+      # pull request, so it would suppress both copies, and `changelog-type:
+      # github` discards the conventional-commit sections.
+      #
+      # This runs on every release rather than being hand-fixed once, because
+      # release-please regenerates both the branch and the notes on every run.
+      # It is a no-op when nothing is duplicated, which is the normal case now
+      # that pull requests are squash-merged.
+      - name: Deduplicate the release changelog
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          RELEASE_BRANCH: release-please--branches--main
+        run: |
+          set -euo pipefail
+
+          # 1. The rolling release pull request.
+          if git ls-remote --exit-code --heads origin "$RELEASE_BRANCH" >/dev/null 2>&1; then
+            git fetch --quiet origin "$RELEASE_BRANCH"
+            git checkout --quiet "$RELEASE_BRANCH"
+            node scripts/dedupe-changelog.mjs CHANGELOG.md
+            if ! git diff --quiet -- CHANGELOG.md; then
+              git config user.name "github-actions[bot]"
+              git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+              git commit -q -m "chore: drop duplicate changelog entries" -- CHANGELOG.md
+              git push origin "$RELEASE_BRANCH"
+            fi
+            git checkout --quiet -
+          fi
+
+          # 2. Any draft release. Its notes are stored separately from
+          #    CHANGELOG.md, so deduplicating one does not touch the other, and
+          #    the draft is what a maintainer actually reads before pressing
+          #    Publish.
+          notes=$(mktemp)
+          for tag in $(gh release list --limit 20 --json tagName,isDraft \
+                        --jq '.[] | select(.isDraft) | .tagName'); do
+            gh release view "$tag" --json body --jq .body > "$notes"
+            node scripts/dedupe-changelog.mjs "$notes"
+            gh release edit "$tag" --notes-file "$notes"
+          done

scripts/dedupe-changelog.mjs

@@ -0,0 +1,107 @@
+#!/usr/bin/env node
+
+/**
+ * Removes duplicate entries from a generated changelog.
+ *
+ * GitHub's "Merge pull request" commits carry the pull request title in their
+ * body:
+ *
+ *   Merge pull request #171 from strapi-community/feat/cache-dashboard
+ *
+ *   feat: add a cache statistics endpoint for the admin dashboard
+ *
+ * release-please parses every conventional commit it finds in a message, so
+ * that body line becomes an entry attributed to the merge commit - and the
+ * commit on the branch underneath produces an identical one. The same change
+ * is listed twice under different shas. There is no config switch for it:
+ * BEGIN_COMMIT_OVERRIDE is keyed on the pull request, so it would suppress
+ * both, and `changelog-type: github` drops the conventional-commit sections.
+ *
+ * This is a one-off. Every pull request since is squash-merged, which produces
+ * a single commit and a single entry, and once this release lands
+ * last-release-sha sits past all 22 merge commits.
+ *
+ * Entries are matched on their text with the trailing ([sha](url)) link
+ * stripped, so the two shas do not defeat the comparison. The first occurrence
+ * wins, which keeps the original ordering.
+ *
+ * Usage:
+ *   node scripts/dedupe-changelog.mjs CHANGELOG.md            # rewrite in place
+ *   node scripts/dedupe-changelog.mjs notes.md --stdout       # print instead
+ *   gh release view v5.1.0-beta --json body -q .body > n.md
+ *     && node scripts/dedupe-changelog.mjs n.md --stdout
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+
+const [, , file, ...flags] = process.argv;
+if (!file) {
+  console.error('usage: dedupe-changelog.mjs <file> [--stdout]');
+  process.exit(1);
+}
+
+const toStdout = flags.includes('--stdout');
+const input = readFileSync(file, 'utf8');
+
+/**
+ * The text of an entry, with the trailing commit link removed.
+ *
+ * `* fix: a thing ([abc1234](https://github.com/o/r/commit/abc1234))`
+ *   -> `fix: a thing`
+ *
+ * Issue links inside the text are deliberately kept: two entries differing
+ * only by which issue they cite are different entries.
+ */
+function entryKey(line) {
+  return line
+    .replace(/^\s*[*-]\s+/, '')
+    .replace(/\s*\(\[[0-9a-f]{7,40}\]\([^)]*\)\)\s*$/, '')
+    .trim()
+    .toLowerCase();
+}
+
+const isEntry = (line) => /^\s*[*-]\s+\S/.test(line);
+// A heading starts a new scope: the same change legitimately appears under
+// both Features and Bug Fixes in different releases, and this file may hold
+// several releases.
+const isHeading = (line) => /^#{1,6}\s/.test(line) || /^<details>/.test(line);
+
+const lines = input.split('\n');
+const out = [];
+let seen = new Set();
+let removed = 0;
+const removedText = [];
+
+for (const line of lines) {
+  if (isHeading(line)) {
+    seen = new Set();
+    out.push(line);
+    continue;
+  }
+
+  if (isEntry(line)) {
+    const key = entryKey(line);
+    if (key && seen.has(key)) {
+      removed += 1;
+      removedText.push(key);
+      continue;
+    }
+    seen.add(key);
+  }
+
+  out.push(line);
+}
+
+const result = out.join('\n');
+
+if (toStdout) {
+  process.stdout.write(result);
+} else {
+  writeFileSync(file, result);
+}
+
+const report = removed
+  ? `removed ${removed} duplicate ${removed === 1 ? 'entry' : 'entries'}:\n` +
+    removedText.map((t) => `  - ${t}`).join('\n')
+  : 'no duplicates found';
+console.error(report);