FileSnapshot#toString: Suppress ReferenceEquality warnings

Reference comparison with EMPTY and MISSING_FILE is intended; these
are static instances used as markers, and will always be the same
instances.

Change-Id: Ic27f5b797bdb9370cf8f6b3b7bb3f1523d4a454c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java

@@ -378,7 +378,7 @@ public class FileSnapshot {
 	}
 
 	/** {@inheritDoc} */
-	@SuppressWarnings("nls")
+	@SuppressWarnings({ "nls", "ReferenceEquality" })
 	@Override
 	public String toString() {
 		if (this == DIRTY) {