fix: preserve frontmatter when updating changelog

fixes absolute-version#106

Signed-off-by: Tim Knight <[email protected]>

Author: TimKnight-DWP

lib/lifecycles/changelog.js

@@ -23,12 +23,21 @@ function outputChangelog (args, newVersion) {
     createIfMissing(args)
     const header = args.header
 
-    let oldContent = args.dryRun || args.releaseCount === 0 ? '' : fs.readFileSync(args.infile, 'utf-8')
-    const oldContentStart = oldContent.search(START_OF_LAST_RELEASE_PATTERN)
+    const oldContent = args.dryRun || args.releaseCount === 0 ? '' : fs.readFileSync(args.infile, 'utf-8')
+
     // find the position of the last release and remove header:
-    if (oldContentStart !== -1) {
-      oldContent = oldContent.substring(oldContentStart)
-    }
+    const oldContentStart = oldContent.search(START_OF_LAST_RELEASE_PATTERN)
+    const oldContentBody =
+        oldContentStart !== -1
+            ? oldContent.substring(oldContentStart)
+            : oldContent;
+
+    const headerStart = oldContent.indexOf(header);
+    const changelogFrontMatter =
+        headerStart !== -1 || headerStart !== 0
+            ? oldContent.substring(0, headerStart)
+            : ''
+
     let content = ''
     const context = { version: newVersion }
     const changelogStream = conventionalChangelog({
@@ -48,7 +57,7 @@ function outputChangelog (args, newVersion) {
     changelogStream.on('end', function () {
       checkpoint(args, 'outputting changes to %s', [args.infile])
       if (args.dryRun) console.info(`\n---\n${chalk.gray(content.trim())}\n---\n`)
-      else writeFile(args, args.infile, header + '\n' + (content + oldContent).replace(/\n+$/, '\n'))
+      else writeFile(args, args.infile, changelogFrontMatter + header + '\n' + (content + oldContentBody).replace(/\n+$/, '\n'))
       return resolve()
     })
   })