1 files changed, 58 insertions, 0 deletions
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/ReachabilityChecker.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/ReachabilityChecker.java
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index 0000000000..5afb669a15
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+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/ReachabilityChecker.java
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+/*
+ * 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.revwalk;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+
+/**
+ * Check if a commit is reachable from a collection of starting commits.
+ * <p>
+ * Note that this checks the reachability of commits (and tags). Trees, blobs or
+ * any other object will cause IncorrectObjectTypeException exceptions.
+ *
+ * @since 5.4
+ */
+public interface ReachabilityChecker {
+	/**
+	 * Check if all targets are reachable from the {@code starters} commits.
+	 * <p>
+	 * Caller should parse the objectIds (preferably with
+	 * {@code walk.parseCommit()} and handle missing/incorrect type objects
+	 * before calling this method.
+	 *
+	 * @param targets
+	 *            commits to reach.
+	 * @param starters
+	 *            known starting points.
+	 * @return An unreachable target if at least one of the targets is
+	 *         unreachable. An empty optional if all targets are reachable from
+	 *         the starters.
+	 *
+	 * @throws MissingObjectException
+	 *             if any of the incoming objects doesn't exist in the
+	 *             repository.
+	 * @throws IncorrectObjectTypeException
+	 *             if any of the incoming objects is not a commit or a tag.
+	 * @throws IOException
+	 *             if any of the underlying indexes or readers can not be
+	 *             opened.
+	 * @since 5.6
+	 */
+	Optional<RevCommit> areAllReachable(Collection<RevCommit> targets,
+			Stream<RevCommit> starters)
+			throws MissingObjectException, IncorrectObjectTypeException,
+			IOException;
+}