RevWalkUtils.java

/*
 * Copyright (C) 2011-2012, Robin Stocker <robin@nibor.org> 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.ArrayList;
import java.util.Collection;
import java.util.List;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.NullProgressMonitor;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;

/**
 * Utility methods for {@link org.eclipse.jgit.revwalk.RevWalk}.
 */
public final class RevWalkUtils {

    private RevWalkUtils() {
        // Utility class
    }

    /**
     * Count the number of commits that are reachable from <code>start</code>
     * until a commit that is reachable from <code>end</code> is encountered. In
     * other words, count the number of commits that are in <code>start</code>,
     * but not in <code>end</code>.
     * <p>
     * Note that this method calls
     * {@link org.eclipse.jgit.revwalk.RevWalk#reset()} at the beginning. Also
     * note that the existing rev filter on the walk is left as-is, so be sure
     * to set the right rev filter before calling this method.
     *
     * @param walk
     *            the rev walk to use
     * @param start
     *            the commit to start counting from
     * @param end
     *            the commit where counting should end, or null if counting
     *            should be done until there are no more commits
     * @return the number of commits
     * @throws org.eclipse.jgit.errors.MissingObjectException
     * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
     * @throws java.io.IOException
     */
    public static int count(final RevWalk walk, final RevCommit start,
            final RevCommit end) throws MissingObjectException,
            IncorrectObjectTypeException, IOException {
        return find(walk, start, end).size();
    }

    /**
     * Find commits that are reachable from <code>start</code> until a commit
     * that is reachable from <code>end</code> is encountered. In other words,
     * Find of commits that are in <code>start</code>, but not in
     * <code>end</code>.
     * <p>
     * Note that this method calls
     * {@link org.eclipse.jgit.revwalk.RevWalk#reset()} at the beginning. Also
     * note that the existing rev filter on the walk is left as-is, so be sure
     * to set the right rev filter before calling this method.
     *
     * @param walk
     *            the rev walk to use
     * @param start
     *            the commit to start counting from
     * @param end
     *            the commit where counting should end, or null if counting
     *            should be done until there are no more commits
     * @return the commits found
     * @throws org.eclipse.jgit.errors.MissingObjectException
     * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
     * @throws java.io.IOException
     */
    public static List<RevCommit> find(final RevWalk walk,
            final RevCommit start, final RevCommit end)
            throws MissingObjectException, IncorrectObjectTypeException,
            IOException {
        walk.reset();
        walk.markStart(start);
        if (end != null)
            walk.markUninteresting(end);

        List<RevCommit> commits = new ArrayList<>();
        for (RevCommit c : walk)
            commits.add(c);
        return commits;
    }

    /**
     * Find the list of branches a given commit is reachable from when following
     * parents.
     * <p>
     * Note that this method calls
     * {@link org.eclipse.jgit.revwalk.RevWalk#reset()} at the beginning.
     * <p>
     * In order to improve performance this method assumes clock skew among
     * committers is never larger than 24 hours.
     *
     * @param commit
     *            the commit we are looking at
     * @param revWalk
     *            The RevWalk to be used.
     * @param refs
     *            the set of branches we want to see reachability from
     * @return the list of branches a given commit is reachable from
     * @throws org.eclipse.jgit.errors.MissingObjectException
     * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
     * @throws java.io.IOException
     */
    public static List<Ref> findBranchesReachableFrom(RevCommit commit,
            RevWalk revWalk, Collection<Ref> refs)
            throws MissingObjectException, IncorrectObjectTypeException,
            IOException {
        return findBranchesReachableFrom(commit, revWalk, refs,
                NullProgressMonitor.INSTANCE);
    }

    /**
     * Find the list of branches a given commit is reachable from when following
     * parents.
     * <p>
     * Note that this method calls
     * {@link org.eclipse.jgit.revwalk.RevWalk#reset()} at the beginning.
     * <p>
     * In order to improve performance this method assumes clock skew among
     * committers is never larger than 24 hours.
     *
     * @param commit
     *            the commit we are looking at
     * @param revWalk
     *            The RevWalk to be used.
     * @param refs
     *            the set of branches we want to see reachability from
     * @param monitor
     *            the callback for progress and cancellation
     * @return the list of branches a given commit is reachable from
     * @throws org.eclipse.jgit.errors.MissingObjectException
     * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
     * @throws java.io.IOException
     * @since 5.4
     */
    public static List<Ref> findBranchesReachableFrom(RevCommit commit,
            RevWalk revWalk, Collection<Ref> refs, ProgressMonitor monitor)
            throws MissingObjectException, IncorrectObjectTypeException,
            IOException {

        // Make sure commit is from the same RevWalk
        commit = revWalk.parseCommit(commit.getId());
        revWalk.reset();
        List<Ref> result = new ArrayList<>();
        monitor.beginTask(JGitText.get().searchForReachableBranches,
                refs.size());
        final int SKEW = 24*3600; // one day clock skew

        for (Ref ref : refs) {
            if (monitor.isCancelled())
                return result;
            monitor.update(1);
            RevObject maybehead = revWalk.parseAny(ref.getObjectId());
            if (!(maybehead instanceof RevCommit))
                continue;
            RevCommit headCommit = (RevCommit) maybehead;

            // if commit is in the ref branch, then the tip of ref should be
            // newer than the commit we are looking for. Allow for a large
            // clock skew.
            if (headCommit.getCommitTime() + SKEW < commit.getCommitTime())
                continue;

            if (revWalk.isMergedInto(commit, headCommit))
                result.add(ref);
        }
        monitor.endTask();
        return result;
    }

}