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 * This program and the accompanying materials are made available
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 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
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package org.eclipse.jgit.revwalk;

import java.io.IOException;
import java.util.Collection;
import java.util.Optional;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;

Check if a commit is reachable from a collection of starting commits.

Note that this checks the reachability of commits (and tags). Trees, blobs or
any other object will cause IncorrectObjectTypeException exceptions.
Since:
5.4/**
 * 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 starter commits. 
 Caller should parse the objectIds (preferably with walk.parseCommit() and handle missing/incorrect type objects before calling this method. 
Params:
targets – 
           commits to reach.
starters – 
           known starting points.
Throws:
MissingObjectException – 
            if any of the incoming objects doesn't exist in the
            repository.
IncorrectObjectTypeException – 
            if any of the incoming objects is not a commit or a tag.
IOException – 
            if any of the underlying indexes or readers can not be
            opened.
Returns:
An unreachable target if at least one of the targets is
        unreachable. An empty optional if all targets are reachable from
        the starters./**
	 * Check if all targets are reachable from the {@code starter} 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.
	 */
	Optional<RevCommit> areAllReachable(Collection<RevCommit> targets,
			Collection<RevCommit> starters)
			throws MissingObjectException, IncorrectObjectTypeException,
			IOException;
}