PatchApplier.Result.Error: mark fields final

Fields of an Error instance shouldn't be modifiable after its creation.
Adapt tests which were setting hh to null to skip asserting it.

Change-Id: I0f55c1d5cd529aa510029054e6f05bd2637d1bca

org.eclipse.jgit.test/tst/org/eclipse/jgit/patch/PatchApplierTest.java

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/patch/PatchApplierTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/patch/PatchApplierTest.java
index eec403a..5507f85 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/patch/PatchApplierTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/patch/PatchApplierTest.java
@@ -373,10 +373,9 @@ public void testConflictMarkers() throws Exception {
 
 			assertEquals(result.getErrors().size(), 1);
 			PatchApplier.Result.Error error = result.getErrors().get(0);
-			error.hh = null; // We don't assert the hunk header as it is a
-								// complex object with lots of internal state.
-			assertEquals(error, new PatchApplier.Result.Error(
-					"cannot apply hunk", "allowconflict", null, true));
+			assertEquals("cannot apply hunk", error.msg);
+			assertEquals("allowconflict", error.oldFileName);
+			assertTrue(error.isGitConflict());
 			verifyChange(result, "allowconflict", true, 1);
 		}
 
@@ -388,10 +387,9 @@ public void testConflictMarkersOutOfBounds() throws Exception {
 
 			assertEquals(result.getErrors().size(), 1);
 			PatchApplier.Result.Error error = result.getErrors().get(0);
-			error.hh = null; // We don't assert the hunk header as it is a
-								// complex object with lots of internal state.
-			assertEquals(error, new PatchApplier.Result.Error(
-					"cannot apply hunk", "ConflictOutOfBounds", null, true));
+			assertEquals("cannot apply hunk", error.msg);
+			assertEquals("ConflictOutOfBounds", error.oldFileName);
+			assertTrue(error.isGitConflict());
 			verifyChange(result, "ConflictOutOfBounds", true, 1);
 		}
 

org.eclipse.jgit/src/org/eclipse/jgit/patch/PatchApplier.java

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/patch/PatchApplier.java b/org.eclipse.jgit/src/org/eclipse/jgit/patch/PatchApplier.java
index 1a98d79..cb6cc6e 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/patch/PatchApplier.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/patch/PatchApplier.java
@@ -177,12 +177,12 @@ public static class Result {
 		// TODO(ms): rename this class in next major release
 		@SuppressWarnings("JavaLangClash")
 		public static class Error {
-			String msg;
+			final String msg;
 
-			String oldFileName;
+			final String oldFileName;
 
 			@Nullable
-			HunkHeader hh;
+			final HunkHeader hh;
 
 			final boolean isGitConflict;