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RefAdvancer: helper to find when a branch enters a pack
For the bitmap calculation in midx, we need to follow a tip until it enters a pack. Add a helper to advance tips until they find their entry point into a pack. Change-Id: I54a7df7dd51be104a31008b3bf2949df6a6a6964
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‎org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/RefAdvancerWalkTest.java‎

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/*
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* Copyright (C) 2026, Google LLC.
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*
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* This program and the accompanying materials are made available under the
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* terms of the Eclipse Distribution License v. 1.0 which is available at
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* https://www.eclipse.org/org/documents/edl-v10.php.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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package org.eclipse.jgit.internal.storage.dfs;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertTrue;
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import java.io.IOException;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.stream.Collectors;
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import org.eclipse.jgit.junit.TestRepository;
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import org.eclipse.jgit.lib.ObjectId;
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import org.eclipse.jgit.revwalk.RevCommit;
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import org.junit.Before;
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import org.junit.Test;
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public class RefAdvancerWalkTest {
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private static final String MAIN = "refs/heads/main";
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private InMemoryRepository db;
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private TestRepository<InMemoryRepository> git;
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private Set<RevCommit> commitsInMidx;
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private Map<String, RevCommit> commitByLetter;
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@Before
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public void setUp() throws Exception {
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db = new InMemoryRepository(
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new DfsRepositoryDescription("ref advance"));
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git = new TestRepository<>(db);
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setupRepo();
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}
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/**
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* <pre>
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* tipMergeBeforeMidx -> H
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* |
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* |
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* F G <- tipStraight
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* |\ |
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* | \|
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* tipMergeMidxCommits -> D E
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* |\ |
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* +--------+
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* | B C <-- tipIn
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* | | / |
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* | |/ |
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* | A |
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* | midx|
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* +--------+
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* </pre>
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*/
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private void setupRepo() throws Exception {
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RevCommit a = commitToMain();
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RevCommit b = commitToMain();
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RevCommit c = commit(a);
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RevCommit d = commitToMain(c);
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RevCommit e = commit(c);
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/* unused */ commitToMain();
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RevCommit g = commit(e);
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RevCommit h = commitToMain();
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commitsInMidx = new HashSet<>();
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commitsInMidx.add(a);
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commitsInMidx.add(b);
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commitsInMidx.add(c);
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commitByLetter = Map.of("a", a, "b", b, "c", c, "d", d, "e", e, "g", g,
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"h", h);
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}
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@Test
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public void singleWant_linearHistory() throws Exception {
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runTest("g", Set.of("c"));
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}
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@Test
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public void singleWant_alreadyInMidx() throws Exception {
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runTest("c", Set.of("c"));
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}
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@Test
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public void singleWant_mergeCommitsInMidx() throws Exception {
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runTest("d", Set.of("b", "c"));
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}
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@Test
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public void singleWant_mergeBeforeMidx() throws Exception {
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runTest("h", Set.of("b", "c"));
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}
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@Test
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public void manyWant_mergeBeforeMidx() throws Exception {
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runTest(Set.of("h", "c", "d", "g"), Set.of("b", "c"));
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}
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private void runTest(String want, Set<String> expectedTips)
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throws IOException {
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runTest(Set.of(want), expectedTips);
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}
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private void runTest(Set<String> want, Set<String> expectedTips)
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throws IOException {
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RefAdvancerWalk advancer = new RefAdvancerWalk(db,
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commitsInMidx::contains);
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List<ObjectId> wants = want.stream().map(commitByLetter::get)
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.collect(Collectors.toUnmodifiableList());
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Set<RevCommit> tipsInMidx = advancer.advance(wants);
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Set<RevCommit> expected = expectedTips.stream().map(commitByLetter::get)
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.collect(Collectors.toUnmodifiableSet());
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assertEquals(expected.size(), tipsInMidx.size());
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assertTrue(tipsInMidx.containsAll(expected));
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}
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private static int commitCounter = 0;
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private RevCommit commitToMain() throws Exception {
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int i = commitCounter++;
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return git.branch(MAIN).commit()
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.add("xx" + i, git.blob("content #" + i)).create();
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}
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private RevCommit commitToMain(RevCommit... extraParent) throws Exception {
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int i = commitCounter++;
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TestRepository<InMemoryRepository>.CommitBuilder commit = git
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.branch(MAIN).commit();
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for (RevCommit p : extraParent) {
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commit.parent(p);
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}
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return commit.add("xx" + i, git.blob("content #" + i)).create();
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}
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private RevCommit commit(RevCommit parent) throws Exception {
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int i = commitCounter++;
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return git.commit().parent(parent)
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.add("cc" + i, git.blob("out of main content #" + i)).create();
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}
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}

‎org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/RefAdvancerWalk.java‎

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/*
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* Copyright (C) 2026, Google LLC.
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*
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* This program and the accompanying materials are made available under the
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* terms of the Eclipse Distribution License v. 1.0 which is available at
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* https://www.eclipse.org/org/documents/edl-v10.php.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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package org.eclipse.jgit.internal.storage.dfs;
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import java.io.IOException;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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import org.eclipse.jgit.errors.StopWalkException;
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import org.eclipse.jgit.lib.ObjectId;
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import org.eclipse.jgit.revwalk.RevCommit;
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import org.eclipse.jgit.revwalk.RevObject;
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import org.eclipse.jgit.revwalk.RevSort;
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import org.eclipse.jgit.revwalk.RevWalk;
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import org.eclipse.jgit.revwalk.filter.RevFilter;
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/**
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* Walk from some commits and find where to they enter a pack
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*/
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class RefAdvancerWalk {
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private final DfsRepository db;
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private final InPackPredicate includeP;
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/**
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* True when the commit is in the pack
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*/
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@FunctionalInterface
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interface InPackPredicate {
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boolean test(RevCommit c) throws IOException;
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}
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RefAdvancerWalk(DfsRepository db, InPackPredicate include) {
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this.db = db;
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this.includeP = include;
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}
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private RevWalk createRevWalk() {
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RevWalk rw = new RevWalk(db);
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rw.sort(RevSort.COMMIT_TIME_DESC);
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rw.setRevFilter(new FirstInPack(includeP));
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return rw;
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}
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/**
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* Advance the tips to their first commit inside the pack
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*
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* @param allTips
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* tips of interesting refs
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* @return first commit(s) where the tips enter the pack. A tips may
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* translate into 0 commits (it doesn't enter the pack in its
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* history), 1 commit (a linear history) or n commits (merges lead
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* to multiple histories into the pack). A tip already inside the
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* pack is returned as it is.
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* @throws IOException
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* error browsing history
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*/
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Set<RevCommit> advance(List<ObjectId> allTips) throws IOException {
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Set<RevCommit> tipsInMidx = new HashSet<>(allTips.size());
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try (RevWalk rw = createRevWalk()) {
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for (ObjectId tip : allTips) {
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RevObject tipObject = rw.parseAny(tip);
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if (!(tipObject instanceof RevCommit tipCommit)) {
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continue;
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}
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rw.markStart(tipCommit);
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RevCommit inPack;
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while ((inPack = rw.next()) != null) {
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tipsInMidx.add(inPack);
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}
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}
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}
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return tipsInMidx;
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}
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private static class FirstInPack extends RevFilter {
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private final InPackPredicate isInPack;
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FirstInPack(InPackPredicate isInPack) {
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this.isInPack = isInPack;
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}
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@Override
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public boolean include(RevWalk walker, RevCommit cmit)
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throws StopWalkException, IOException {
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if (!isInPack.test(cmit)) {
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return false;
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}
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for (RevCommit p : cmit.getParents()) {
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walker.markUninteresting(p);
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}
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return true;
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}
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@Override
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public RevFilter clone() {
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return this;
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}
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}
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}

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