Clarifying comments

syncany-lib/src/main/java/org/syncany/database/dao/FileHistorySqlDao.java

@@ -247,13 +247,18 @@ public PartialFileHistory getFileHistoryWithLastVersionByPath(String path) {
 					return null;
 				}
 
-				// Find for the latest file history the last file version to check if the file has moved
+				// Get the last FileVersion of the FileHistory in the database with the largest vectorclock.
 				PartialFileHistory fileHistory = getLastVersionByFileHistoryId(latestFileHistoryId);
 
+				// The above query does not guarantee the resulting version is the last in its
+				// history. We need to check this before returning the file.
 				if (fileHistory.getLastVersion().getVersion() == latestFileVersion) {
 					return fileHistory;
 				}
 				else {
+					// The version retrieved by the path query is not a fileversion which is in the current
+					// filetree. Since it was the last version with this path, there is no other history
+					// which should be continued.
 					return null;
 				}
 			}

syncany-lib/src/main/resources/org/syncany/database/sql/filehistory.select.master.findLatestFileVersionsForPath.sql

@@ -7,7 +7,10 @@
 -- - Rule out deleted versions (where)
 -- 
 -- Please note: It is important that the initial inner select (fvmax) does not rule out deleted versions, as this has caused trouble in the past
-
+--
+-- Note that we only select the newest version from every filehistory, since we use this query to
+-- find filehistories to build on, so older versions are not needed. In addition, we only consider
+-- versions in MASTER, since we can't build on DIRTY databases.
 SELECT fvmax.version AS version,
   fvmax.filehistory_id AS filehistory_id,
   dbv.vectorclock_serialized AS vectorclock_serialized