Adds an enum to describe how PackageLookupFunction should handle package labels
which cross into a sub-repository. Part of #1592.

--
MOS_MIGRATED_REVID=135931868
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
index a64ec6d..1ec88f5 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
@@ -37,6 +37,7 @@
 import com.google.devtools.build.lib.events.NullEventHandler;
 import com.google.devtools.build.lib.pkgcache.PathPackageLocator;
 import com.google.devtools.build.lib.skyframe.DirtinessCheckerUtils.BasicFilesystemDirtinessChecker;
+import com.google.devtools.build.lib.skyframe.PackageLookupFunction.CrossRepositoryLabelViolationStrategy;
 import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
@@ -113,8 +114,11 @@
         new FileSymlinkInfiniteExpansionUniquenessFunction());
     skyFunctions.put(SkyFunctions.PACKAGE,
         new PackageFunction(null, null, null, null, null, null, null));
-    skyFunctions.put(SkyFunctions.PACKAGE_LOOKUP,
-        new PackageLookupFunction(new AtomicReference<>(ImmutableSet.<PackageIdentifier>of())));
+    skyFunctions.put(
+        SkyFunctions.PACKAGE_LOOKUP,
+        new PackageLookupFunction(
+            new AtomicReference<>(ImmutableSet.<PackageIdentifier>of()),
+            CrossRepositoryLabelViolationStrategy.ERROR));
     skyFunctions.put(SkyFunctions.WORKSPACE_AST,
         new WorkspaceASTFunction(TestRuleClassProvider.getRuleClassProvider()));
     skyFunctions.put(SkyFunctions.WORKSPACE_FILE,