1 files changed, 70 insertions, 0 deletions
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/revwalk/PedestrianReachabilityChecker.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/revwalk/PedestrianReachabilityChecker.java
new file mode 100644
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+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/revwalk/PedestrianReachabilityChecker.java
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2019, 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.internal.revwalk;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.revwalk.ReachabilityChecker;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevSort;
+import org.eclipse.jgit.revwalk.RevWalk;
+
+/**
+ * Checks the reachability walking the graph from the starters towards the
+ * target.
+ */
+public class PedestrianReachabilityChecker implements ReachabilityChecker {
+
+	private final boolean topoSort;
+
+	private final RevWalk walk;
+
+	/**
+	 * New instance of the reachability checker using a existing walk.
+	 *
+	 * @param topoSort
+	 *            walk commits in topological order
+	 * @param walk
+	 *            RevWalk instance to reuse. Caller retains ownership.
+	 */
+	public PedestrianReachabilityChecker(boolean topoSort,
+			RevWalk walk) {
+		this.topoSort = topoSort;
+		this.walk = walk;
+	}
+
+	@Override
+	public Optional<RevCommit> areAllReachable(Collection<RevCommit> targets,
+			Stream<RevCommit> starters)
+					throws MissingObjectException, IncorrectObjectTypeException,
+					IOException {
+		walk.reset();
+		if (topoSort) {
+			walk.sort(RevSort.TOPO);
+		}
+
+		for (RevCommit target: targets) {
+			walk.markStart(target);
+		}
+
+		Iterator<RevCommit> iterator = starters.iterator();
+		while (iterator.hasNext()) {
+			walk.markUninteresting(iterator.next());
+		}
+
+		return Optional.ofNullable(walk.next());
+	}
+}