1 files changed, 143 insertions, 0 deletions
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/ObjectReachabilityTestCase.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/ObjectReachabilityTestCase.java
new file mode 100644
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@@ -0,0 +1,143 @@
+/*
+ * Copyright (C) 2020, Google LLC and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.revwalk;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+import org.eclipse.jgit.internal.storage.file.FileRepository;
+import org.eclipse.jgit.junit.LocalDiskRepositoryTestCase;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.junit.TestRepository.CommitBuilder;
+import org.junit.Before;
+import org.junit.Test;
+
+public abstract class ObjectReachabilityTestCase
+		extends LocalDiskRepositoryTestCase {
+
+	private TestRepository<FileRepository> repo;
+	private AddressableRevCommit baseCommit;
+	private AddressableRevCommit branchACommit;
+	private AddressableRevCommit branchBCommit;
+	private AddressableRevCommit mergeCommit;
+
+	abstract ObjectReachabilityChecker getChecker(
+			TestRepository<FileRepository> repository) throws Exception;
+
+	// Pair of commit and blob inside it
+	protected static class AddressableRevCommit {
+		RevCommit commit;
+
+		RevBlob blob;
+
+		AddressableRevCommit(RevCommit commit, RevBlob blob) {
+			this.commit = commit;
+			this.blob = blob;
+		}
+	}
+
+	/** {@inheritDoc} */
+	@Override
+	@Before
+	public void setUp() throws Exception {
+		super.setUp();
+		FileRepository db = createWorkRepository();
+		repo = new TestRepository<>(db);
+		prepareRepo();
+	}
+
+	@Test
+	public void blob_in_base_reachable_from_branches() throws Exception {
+		ObjectReachabilityChecker checker = getChecker(repo);
+
+		RevObject baseBlob = baseCommit.blob;
+		assertReachable("reachable from one branch", checker.areAllReachable(
+				Arrays.asList(baseBlob), Stream.of(branchACommit.commit)));
+		assertReachable("reachable from another branch",
+				checker.areAllReachable(
+						Arrays.asList(baseBlob),
+						Stream.of(branchBCommit.commit)));
+	}
+
+	@Test
+	public void blob_reachable_from_owning_commit() throws Exception {
+		ObjectReachabilityChecker checker = getChecker(repo);
+
+		RevObject branchABlob = branchACommit.blob;
+		assertReachable("reachable from itself",
+				checker.areAllReachable(Arrays.asList(branchABlob),
+						Stream.of(branchACommit.commit)));
+	}
+
+	@Test
+	public void blob_in_branch_reachable_from_merge() throws Exception {
+		ObjectReachabilityChecker checker = getChecker(repo);
+
+		RevObject branchABlob = branchACommit.blob;
+		assertReachable("reachable from merge", checker.areAllReachable(
+				Arrays.asList(branchABlob), Stream.of(mergeCommit.commit)));
+	}
+
+	@Test
+	public void blob_unreachable_from_earlier_commit() throws Exception {
+		ObjectReachabilityChecker checker = getChecker(repo);
+
+		RevObject branchABlob = branchACommit.blob;
+		assertUnreachable("unreachable from earlier commit",
+				checker.areAllReachable(Arrays.asList(branchABlob),
+						Stream.of(baseCommit.commit)));
+	}
+
+	@Test
+	public void blob_unreachable_from_parallel_branch() throws Exception {
+		ObjectReachabilityChecker checker = getChecker(repo);
+
+		RevObject branchABlob = branchACommit.blob;
+		assertUnreachable("unreachable from another branch",
+				checker.areAllReachable(Arrays.asList(branchABlob),
+						Stream.of(branchBCommit.commit)));
+	}
+
+	private void prepareRepo() throws Exception {
+		baseCommit = createCommit("base");
+		branchACommit = createCommit("branchA", baseCommit);
+		branchBCommit = createCommit("branchB", baseCommit);
+		mergeCommit = createCommit("merge", branchACommit, branchBCommit);
+
+		// Bitmaps are generated from references
+		repo.update("refs/heads/a", branchACommit.commit);
+		repo.update("refs/heads/b", branchBCommit.commit);
+		repo.update("refs/heads/merge", mergeCommit.commit);
+	}
+
+	private AddressableRevCommit createCommit(String blobPath, AddressableRevCommit... parents) throws Exception {
+		RevBlob blob = repo.blob(blobPath + " content");
+		CommitBuilder commitBuilder = repo.commit();
+		for (int i = 0; i < parents.length; i++) {
+			commitBuilder.parent(parents[i].commit);
+		}
+		commitBuilder.add(blobPath, blob);
+
+		RevCommit commit = commitBuilder.create();
+		return new AddressableRevCommit(commit, blob);
+	}
+
+	private static void assertReachable(String msg, Optional<RevObject> result) {
+		assertFalse(msg, result.isPresent());
+	}
+
+	private static void assertUnreachable(String msg, Optional<RevObject> result) {
+		assertTrue(msg, result.isPresent());
+	}
+}
+\ No newline at end of file