Fix RevWalkUtils.findBranchesReachableFrom not finding some branches

The "cut off" optimization causes it to not include branches that
contain the specified commit but happen to share commits with a branch
that does not contain the commit.

An example:

      -B foo
        \
    -A---C master

findBranchesReachableFrom for commit A with both branches as input may
not return master (depending on the order of the input). The reason is
that A is not contained in foo, and therefore the old code would put B
in the cutOff set. When then walking the master commits and B is
checked, it is found in the cutOff set and the walk is aborted, causing
master not to be returned even though it should.

Bug: 425674
Change-Id: I2c0c406ce5fcc9a03538b483473af930d4895d30
Signed-off-by: Robin Stocker <robin@nibor.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevWalkUtilsReachableTest.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) 2014, Robin Stocker <robin@nibor.org>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.revwalk;
+
+import static java.util.Arrays.asList;
+import static org.junit.Assert.assertEquals;
+
+import java.util.Collection;
+import java.util.List;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.RefComparator;
+import org.junit.Test;
+
+public class RevWalkUtilsReachableTest extends RevWalkTestCase {
+
+	@Test
+	public void oneCommit() throws Exception {
+		RevCommit a = commit();
+		Ref branchA = branch("a", a);
+
+		assertContains(a, asList(branchA));
+	}
+
+	@Test
+	public void twoCommits() throws Exception {
+		RevCommit a = commit();
+		RevCommit b = commit(a);
+		branch("a", a);
+		Ref branchB = branch("b", b);
+
+		assertContains(b, asList(branchB));
+	}
+
+	@Test
+	public void multipleBranches() throws Exception {
+		RevCommit a = commit();
+		RevCommit b = commit(a);
+		branch("a", a);
+		Ref branchB = branch("b", b);
+		Ref branchB2 = branch("b2", b);
+
+		assertContains(b, asList(branchB, branchB2));
+	}
+
+	@Test
+	public void withMerge() throws Exception {
+		RevCommit a = commit();
+		RevCommit b = commit();
+		RevCommit c = commit(a, b);
+		Ref branchA = branch("a", a);
+		Ref branchB = branch("b", b);
+		Ref branchC = branch("c", c);
+
+		assertContains(a, asList(branchA, branchC));
+		assertContains(b, asList(branchB, branchC));
+	}
+
+	@Test
+	public void withCommitLoadedByDifferentRevWalk() throws Exception {
+		RevCommit a = commit();
+		Ref branchA = branch("a", a);
+
+		RevWalk walk = new RevWalk(db);
+		try {
+			RevCommit parsedCommit = walk.parseCommit(a.getId());
+			assertContains(parsedCommit, asList(branchA));
+		} finally {
+			walk.release();
+		}
+	}
+
+	private Ref branch(final String name, final RevCommit dst) throws Exception {
+		return Git.wrap(db).branchCreate().setName(name)
+				.setStartPoint(dst.name()).call();
+	}
+
+	private void assertContains(RevCommit commit, Collection<Ref> refsThatShouldContainCommit) throws Exception {
+		Collection<Ref> allRefs = db.getAllRefs().values();
+		Collection<Ref> sortedRefs = RefComparator.sort(allRefs);
+		List<Ref> actual = RevWalkUtils.findBranchesReachableFrom(commit,
+				rw, sortedRefs);
+		assertEquals(refsThatShouldContainCommit, actual);
+	}
+
+}

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalkUtils.java

@@ -45,15 +45,11 @@ package org.eclipse.jgit.revwalk;
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
-import org.eclipse.jgit.lib.AnyObjectId;
-import org.eclipse.jgit.lib.ObjectId;
-import org.eclipse.jgit.lib.ObjectIdSubclassMap;
 import org.eclipse.jgit.lib.Ref;
 
 /**
@@ -156,11 +152,10 @@ public final class RevWalkUtils {
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException {
 
+		// Make sure commit is from the same RevWalk
+		commit = revWalk.parseCommit(commit.getId());
+		revWalk.reset();
 		List<Ref> result = new ArrayList<Ref>();
-		// searches from branches can be cut off early if any parent of the
-		// search-for commit is found. This is quite likely, so optimize for this.
-		revWalk.markStart(Arrays.asList(commit.getParents()));
-		ObjectIdSubclassMap<ObjectId> cutOff = new ObjectIdSubclassMap<ObjectId>();
 
 		final int SKEW = 24*3600; // one day clock skew
 
@@ -176,26 +171,8 @@ public final class RevWalkUtils {
 			if (headCommit.getCommitTime() + SKEW < commit.getCommitTime())
 				continue;
 
-			List<ObjectId> maybeCutOff = new ArrayList<ObjectId>(cutOff.size()); // guess rough size
-			revWalk.resetRetain();
-			revWalk.markStart(headCommit);
-			RevCommit current;
-			Ref found = null;
-			while ((current = revWalk.next()) != null) {
-				if (AnyObjectId.equals(current, commit)) {
-					found = ref;
-					break;
-				}
-				if (cutOff.contains(current))
-					break;
-				maybeCutOff.add(current.toObjectId());
-			}
-			if (found != null)
+			if (revWalk.isMergedInto(commit, headCommit))
 				result.add(ref);
-			else
-				for (ObjectId id : maybeCutOff)
-					cutOff.addIfAbsent(id);
-
 		}
 		return result;
 	}