reftable: compact merged tables

A compaction of reftables is just copying the results of a
MergedReftable into a ReftableWriter.  Wrap this up into a utility.

Change-Id: I6f5677d923e9628993a2d8b4b007a9b8662c9045

1 files changed, 27 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/MergedReftableTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/MergedReftableTest.java
index b6306d09e4..f9ebaf6926 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/MergedReftableTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/MergedReftableTest.java
@@ -261,6 +261,33 @@ public class MergedReftableTest {
 		}
 	}
 
+	@Test
+	public void compaction() throws IOException {
+		List<Ref> delta1 = Arrays.asList(
+				ref("refs/heads/next", 4),
+				ref("refs/heads/master", 1));
+		List<Ref> delta2 = Arrays.asList(delete("refs/heads/next"));
+		List<Ref> delta3 = Arrays.asList(ref("refs/heads/master", 8));
+
+		ReftableCompactor compactor = new ReftableCompactor();
+		compactor.addAll(Arrays.asList(
+				read(write(delta1)),
+				read(write(delta2)),
+				read(write(delta3))));
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		compactor.compact(out);
+		byte[] table = out.toByteArray();
+
+		ReftableReader reader = read(table);
+		try (RefCursor rc = reader.allRefs()) {
+			assertTrue(rc.next());
+			Ref r = rc.getRef();
+			assertEquals("refs/heads/master", r.getName());
+			assertEquals(id(8), r.getObjectId());
+			assertFalse(rc.next());
+		}
+	}
+
 	private static MergedReftable merge(byte[]... table) {
 		List<Reftable> stack = new ArrayList<>(table.length);
 		for (byte[] b : table) {