Why does this patch applied with a fuzz of 1, and fail with fuzz of 0?

Question

$ vim patch
Index: toPatch
===================================================================
--- toPatch
+++ toPatch
@@ -2,4 +2,4 @@
  */
-final public class XMLWriter {
+public class XMLWriter {

$ vim toPatch
 */
final public class XMLWriter {

  public static float CURRENT_VERSION=2.2f;
    $ patch -p0 -ui patch
patching file toPatch
Hunk #1 succeeded at 1 with fuzz 2 (offset -1 lines).

Why the fuzz and the line offset? This is a demo case trying to understand diff and patch, since tools sometimes/often don't seem to work as expected.

Answer 1

Patch does some basic checking of consistency of the diff and your file, and if these checks fail, you get offset or fuzz.

You have offset -1, since patch expects the contents of the diff match lines 2--4 of your file. In your file, however, they are lines 1--3.

You have fuzz>0, since the first line of the context (two spaces and a */) does not match the line in the actual file (one space and a */). Because of that, patch did a second pass where it ignored the first and the last line of the context.

This doesn't explain why you see fuzz=2 and not 1. Maybe an error copy-pasting the files? Any other ideas, anybody?