Mark no file with /dev/null to align with git diff (#93)

MTelling · web-flow · commit d3524314eb9c · 2020-08-04T07:29:55.000+02:00
If you run git diff locally with a staged new file the diff will indicate that the file did not exist before with `--- /dev/null`.
I believe this should align with this?
diff --git a/java-diff-utils/src/main/java/com/github/difflib/UnifiedDiffUtils.java b/java-diff-utils/src/main/java/com/github/difflib/UnifiedDiffUtils.java
@@ -33,6 +33,7 @@ public final class UnifiedDiffUtils {
 
     private static final Pattern UNIFIED_DIFF_CHUNK_REGEXP = Pattern
             .compile("^@@\\s+-(?:(\\d+)(?:,(\\d+))?)\\s+\\+(?:(\\d+)(?:,(\\d+))?)\\s+@@$");
+    private static final String NULL_FILE_INDICATOR = "/dev/null";
 
     /**
      * Parse the given text in unified format and creates the list of deltas for it.
@@ -143,8 +144,8 @@ public static List<String> generateUnifiedDiff(String originalFileName,
             int contextSize) {
         if (!patch.getDeltas().isEmpty()) {
             List<String> ret = new ArrayList<>();
-            ret.add("--- " + Optional.ofNullable(originalFileName).orElse(""));
-            ret.add("+++ " + Optional.ofNullable(revisedFileName).orElse(""));
+            ret.add("--- " + Optional.ofNullable(originalFileName).orElse(NULL_FILE_INDICATOR));
+            ret.add("+++ " + Optional.ofNullable(revisedFileName).orElse(NULL_FILE_INDICATOR));
 
             List<AbstractDelta<String>> patchDeltas = new ArrayList<>(
                     patch.getDeltas());
