Fix comments regarding rpackages when a file has no ancestor BUILD file
@@ -173,6 +173,9 @@ public class RBuildFilesVisitor extends ParallelQueryVisitor<SkyKey, PackageIden
* of SkyKeys whose transitive reverse dependencies must contain the exact same set of packages.
*
* <p>Note that there may not be nodes in the graph corresponding to the returned SkyKeys.
+ *
+ * <p>Note also that we assume there'll be a PackageLookupValue node for some ancestor directory
+ * of every file to which a symlink could possibly point otherwise the file will not be included.
*/
private static Collection<SkyKey> getSkyKeysForFileFragments(
WalkableGraph graph, Iterable<PathFragment> pathFragments) throws InterruptedException {
