fix: end changelog version entry with empty line

Append an empty line to the changelog entry when writing it to the
changelog file, to ensure there's an empty line above the next version
entry.

Fixes #65

Signed-off-by: Matthew Weier O'Phinney <[email protected]>

Author: weierophinney

src/Changelog/ChangelogReleaseNotes.php

@@ -9,6 +9,8 @@
 use RuntimeException;
 use Webmozart\Assert\Assert;
 
+use function rtrim;
+
 /**
  * @psalm-immutable
  */
@@ -33,10 +35,12 @@ public static function writeChangelogFile(string $changelogFile, self $releaseNo
 
         Assert::notNull($releaseNotes->changelogEntry);
 
+        $changelogEntry = rtrim($releaseNotes->contents, "\n") . "\n\n";
+
         $editor = new ChangelogEditor();
         $editor->update(
             $changelogFile,
-            $releaseNotes->contents,
+            $changelogEntry,
             $releaseNotes->changelogEntry
         );
     }

test/unit/Changelog/ChangelogReleaseNotesTest.php

@@ -98,7 +98,7 @@ public function testWriteChangelogRewritesFileWithNewContents(): void
         $contents = file_get_contents($filename);
 
         $this->assertStringContainsString($requiredString, $contents);
-        $this->assertStringContainsString($releaseNotes->contents(), $contents);
+        $this->assertStringContainsString($releaseNotes->contents() . "\n", $contents);
     }
 
     public function testMergeRaisesExceptionIfBothCurrentAndNextInstanceContainChangelogEntries(): void