refactor: address PR #288 comments

src/main/java/com/conveyal/datatools/manager/jobs/MergeFeedsJob.java

@@ -134,6 +134,10 @@ public class MergeFeedsJob extends MonitorableJob {
     public final String projectId;
     public final MergeFeedsType mergeType;
     private File mergedTempFile = null;
+    /**
+     * If {@link MergeFeedsJob} storeNewVersion variable is true, a new version will be created from the merged GTFS
+     * dataset. Otherwise, this will be null throughout the life of the job.
+     */
     final FeedVersion mergedVersion;
     public boolean failOnDuplicateTripId = true;
 

src/main/java/com/conveyal/datatools/manager/jobs/MergeFeedsType.java

@@ -1,6 +1,14 @@
 package com.conveyal.datatools.manager.jobs;
 
+/**
+ * This enum contains the types of merge feeds that {@link MergeFeedsJob} can currently perform.
+ */
 public enum MergeFeedsType {
+    /** Merge feed versions that represent different transit agencies (usually operating in the same geographic region */
     REGIONAL,
+    /**
+     * Merge two feed versions from the same transit agency that contain service for different time periods (usually to
+     * combine two overlapping time periods, for example, the current schedules and the future schedules).
+     */
     SERVICE_PERIOD
 }