CommitGraphWriter: Move path diff calculation to its own class

To verify that we have the right paths between commits we are writing
the bloom filters, reading them and querying. The path diff
calculation is tricky enough for correctness and performance that
should be tested on its own.

Move the path diff calculation to its own class, so we can test it on
its own.

This is a noop refactor so we can verify later the steps taken in the
walk.

Change-Id: Ifbdcb752891c4adb08553802f87287de1155bb7c

1 files changed, 24 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriterTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriterTest.java
index 9f65ee2074..7130d59b95 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriterTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriterTest.java
@@ -10,6 +10,7 @@
 
 package org.eclipse.jgit.internal.storage.commitgraph;
 
+import static java.util.stream.Collectors.toList;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.junit.Assert.assertArrayEquals;
@@ -19,8 +20,12 @@ import static org.junit.Assert.assertTrue;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 
 import org.eclipse.jgit.dircache.DirCacheEntry;
@@ -413,6 +418,25 @@ public class CommitGraphWriterTest extends RepositoryTestCase {
 				"119,69,63,-8,0,"));
 	}
 
+	@Test
+	public void testPathDiffCalculator_skipUnchangedTree() throws Exception {
+		RevCommit root = tr.commit(tr.tree(
+				tr.file("d/sd1/f1", tr.blob("f1")),
+				tr.file("d/sd2/f2", tr.blob("f2"))));
+		RevCommit tip = tr.commit(tr.tree(
+				tr.file("d/sd1/f1", tr.blob("f1")),
+				tr.file("d/sd2/f2", tr.blob("f2B"))), root);
+		CommitGraphWriter.PathDiffCalculator c = new CommitGraphWriter.PathDiffCalculator();
+
+		Optional<HashSet<ByteBuffer>> byteBuffers = c.changedPaths(walk.getObjectReader(), tip);
+
+		assertTrue(byteBuffers.isPresent());
+		List<String> asString = byteBuffers.get().stream()
+				.map(b -> StandardCharsets.UTF_8.decode(b).toString())
+				.collect(toList());
+		assertThat(asString, containsInAnyOrder("d", "d/sd2", "d/sd2/f2"));
+	}
+
 	RevCommit commit(RevCommit... parents) throws Exception {
 		return tr.commit(parents);
 	}