Prevent duplicate changelog entries (#10786)

The changelog update script now prevents duplicate entries from being
added. Specifically, it will ensure that if a PR has been referenced
already in an entry, it will not add it again.

This should prevent it from adding duplicate entries for changes that
were cherry-picked into hotfix releases.

Note that this duplication prevention only works for entries containing
a PR number. We don't have any way to prevent duplicate entries yet in
cases where we don't know the associated PR. We will be preventing this
possibility entirely pretty soon in some upcoming release automation
changes though, so I'm not concerned about this omission.

Author: Gudahtt

development/auto-changelog.js

@@ -27,7 +27,7 @@ async function main() {
     `${mostRecentTag}..HEAD`,
   ]);
 
-  const changelogEntries = [];
+  const commitEntries = [];
   for (const commit of commitsSinceLastRelease) {
     const [subject] = await runCommand('git', [
       'show',
@@ -36,20 +36,20 @@ async function main() {
       commit,
     ]);
 
-    let prefix;
+    let prNumber;
     let description = subject;
 
     // Squash & Merge: the commit subject is parsed as `<description> (#<PR ID>)`
     if (subject.match(/\(#\d+\)/u)) {
-      const [, prNumber] = subject.match(/\(#(\d+)\)/u);
-      prefix = `[#${prNumber}](${URL}/pull/${prNumber})`;
+      const matchResults = subject.match(/\(#(\d+)\)/u);
+      prNumber = matchResults[1];
       description = subject.match(/^(.+)\s\(#\d+\)/u)[1];
       // Merge: the PR ID is parsed from the git subject (which is of the form `Merge pull request
       // #<PR ID> from <branch>`, and the description is assumed to be the first line of the body.
       // If no body is found, the description is set to the commit subject
     } else if (subject.match(/#\d+\sfrom/u)) {
-      const [, prNumber] = subject.match(/#(\d+)\sfrom/u);
-      prefix = `[#${prNumber}](${URL}/pull/${prNumber})`;
+      const matchResults = subject.match(/#(\d+)\sfrom/u);
+      prNumber = matchResults[1];
       const [firstLineOfBody] = await runCommand('git', [
         'show',
         '-s',
@@ -61,10 +61,7 @@ async function main() {
     // Otherwise:
     // Normal commits: The commit subject is the description, and the PR ID is omitted.
 
-    const changelogEntry = prefix
-      ? `- ${prefix}: ${description}`
-      : `- ${description}`;
-    changelogEntries.push(changelogEntry);
+    commitEntries.push({ prNumber, description });
   }
 
   const changelogFilename = path.resolve(__dirname, '..', 'CHANGELOG.md');
@@ -93,6 +90,33 @@ async function main() {
       }'`,
     );
   }
+
+  const prNumbersWithChangelogEntries = [];
+  for (const line of changelogLines) {
+    const matchResults = line.match(/- \[#(\d+)\]/u);
+    if (matchResults === null) {
+      continue;
+    }
+    const prNumber = matchResults[1];
+    prNumbersWithChangelogEntries.push(prNumber);
+  }
+
+  const changelogEntries = [];
+  for (const { prNumber, description } of commitEntries) {
+    if (prNumbersWithChangelogEntries.includes(prNumber)) {
+      continue;
+    }
+
+    let changelogEntry;
+    if (prNumber) {
+      const prefix = `[#${prNumber}](${URL}/pull/${prNumber})`;
+      changelogEntry = `- ${prefix}: ${description}`;
+    } else {
+      changelogEntry = `- ${description}`;
+    }
+    changelogEntries.push(changelogEntry);
+  }
+
   changelogLines.splice(releaseHeaderIndex + 1, 0, ...changelogEntries);
   const updatedChangelog = changelogLines.join('\n');
   await fs.writeFile(changelogFilename, updatedChangelog);