Merge pull request #2376 from chrisism/hotfix/merge_message_format_issue

Added simple fix for mergemessageformats override

Author: asbjornu

src/GitVersionCore/Configuration/ConfigurationBuilder.cs

@@ -60,7 +60,7 @@ private static void ApplyOverrides([NotNull] Config targetConfig, [NotNull] Conf
             targetConfig.CommitMessageIncrementing = overrideConfig.CommitMessageIncrementing ?? targetConfig.CommitMessageIncrementing;
             targetConfig.Increment = overrideConfig.Increment ?? targetConfig.Increment;
             targetConfig.CommitDateFormat = overrideConfig.CommitDateFormat ?? targetConfig.CommitDateFormat;
-            targetConfig.MergeMessageFormats = overrideConfig.MergeMessageFormats ?? targetConfig.MergeMessageFormats;
+            targetConfig.MergeMessageFormats = overrideConfig.MergeMessageFormats.Any() ? overrideConfig.MergeMessageFormats : targetConfig.MergeMessageFormats;
             targetConfig.UpdateBuildNumber = overrideConfig.UpdateBuildNumber ?? targetConfig.UpdateBuildNumber;
 
             if (overrideConfig.Ignore != null && !overrideConfig.Ignore.IsEmpty)