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// Copyright (C) 2020 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.server.patch;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.entities.Project;
import com.google.gerrit.entities.RefNames;
import com.google.gerrit.git.LockFailureException;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.InMemoryInserter;
import com.google.gerrit.server.update.RepoView;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.util.Optional;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevObject;
import org.eclipse.jgit.revwalk.RevWalk;
/** A utility class for computing the base commit / parent for a specific patchset commit. */
@Singleton
class BaseCommitUtil {
private final AutoMerger autoMerger;
private final GitRepositoryManager repoManager;
/** If true, auto-merge results are stored in the repository. */
private final boolean saveAutomerge;
@Inject
BaseCommitUtil(AutoMerger am, @GerritServerConfig Config cfg, GitRepositoryManager repoManager) {
this.autoMerger = am;
this.saveAutomerge = AutoMerger.cacheAutomerge(cfg);
this.repoManager = repoManager;
}
RevObject getBaseCommit(Project.NameKey project, ObjectId newCommit, @Nullable Integer parentNum)
throws IOException {
try (Repository repo = repoManager.openRepository(project);
ObjectInserter ins = newInserter(repo);
ObjectReader reader = ins.newReader();
RevWalk rw = new RevWalk(reader)) {
return getParentCommit(repo, ins, rw, parentNum, newCommit);
}
}
/**
* Returns the number of parent commits of the commit represented by the commitId parameter.
*
* @param project a specific git repository.
* @param commitId 20 bytes commitId SHA-1 hash.
* @return an integer representing the number of parents of the designated commit.
*/
int getNumParents(Project.NameKey project, ObjectId commitId) throws IOException {
try (Repository repo = repoManager.openRepository(project);
ObjectInserter ins = repo.newObjectInserter();
ObjectReader reader = ins.newReader();
RevWalk rw = new RevWalk(reader)) {
RevCommit current = rw.parseCommit(commitId);
return current.getParentCount();
}
}
/**
* Returns the parent commit Object of the commit represented by the commitId parameter.
*
* @param repo a git repository.
* @param ins a git object inserter in the database.
* @param rw a {@link RevWalk} object of the repository.
* @param parentNum used to identify the parent number for merge commits. If parentNum is null and
* {@code commitId} has two parents, the auto-merge commit will be returned. If {@code
* commitId} has a single parent, it will be returned.
* @param commitId 20 bytes commitId SHA-1 hash.
* @return Returns the parent commit of the commit represented by the commitId parameter. Note
* that auto-merge is not supported for commits having more than two parents.
*/
RevObject getParentCommit(
Repository repo,
ObjectInserter ins,
RevWalk rw,
@Nullable Integer parentNum,
ObjectId commitId)
throws IOException {
RevCommit current = rw.parseCommit(commitId);
switch (current.getParentCount()) {
case 0:
return rw.parseAny(emptyTree(ins));
case 1:
return current.getParent(0);
default:
if (parentNum != null) {
RevCommit r = current.getParent(parentNum - 1);
rw.parseBody(r);
return r;
}
// Only support auto-merge for 2 parents, not octopus merges
if (current.getParentCount() == 2) {
if (!saveAutomerge) {
throw new IOException(
"diff against auto-merge commits is only supported if 'change.cacheAutomerge' config is set to true.");
}
// TODO(ghareeb): Avoid persisting auto-merge commits.
return getAutoMergeFromGitOrCreate(repo, ins, rw, current);
}
return null;
}
}
/**
* Gets the auto-merge commit from git if it already exists. If not, the auto-merge is created,
* persisted in git and the cache-automerge ref is updated for the merge commit.
*
* @return the auto-merge {@link RevCommit}
*/
private RevCommit getAutoMergeFromGitOrCreate(
Repository repo, ObjectInserter ins, RevWalk rw, RevCommit mergeCommit) throws IOException {
String refName = RefNames.refsCacheAutomerge(mergeCommit.name());
Optional autoMergeCommit = autoMerger.lookupCommit(repo, rw, refName);
if (autoMergeCommit.isPresent()) {
return autoMergeCommit.get();
}
ObjectId autoMergeId =
autoMerger.createAutoMergeCommit(new RepoView(repo, rw, ins), rw, ins, mergeCommit);
ins.flush();
return updateRef(repo, rw, refName, autoMergeId, mergeCommit);
}
private static RevCommit updateRef(
Repository repo, RevWalk rw, String refName, ObjectId autoMergeId, RevCommit merge)
throws IOException {
RefUpdate ru = repo.updateRef(refName);
ru.setNewObjectId(autoMergeId);
ru.disableRefLog();
switch (ru.forceUpdate()) {
case FAST_FORWARD:
case FORCED:
case NEW:
case NO_CHANGE:
return rw.parseCommit(autoMergeId);
case LOCK_FAILURE:
throw new LockFailureException(
String.format("Failed to create auto-merge of %s", merge.name()), ru);
case IO_FAILURE:
case NOT_ATTEMPTED:
case REJECTED:
case REJECTED_CURRENT_BRANCH:
case REJECTED_MISSING_OBJECT:
case REJECTED_OTHER_REASON:
case RENAMED:
default:
throw new IOException(
String.format(
"Failed to create auto-merge of %s: Cannot write %s (%s)",
merge.name(), refName, ru.getResult()));
}
}
private ObjectInserter newInserter(Repository repo) {
return saveAutomerge ? repo.newObjectInserter() : new InMemoryInserter(repo);
}
private static ObjectId emptyTree(ObjectInserter ins) throws IOException {
ObjectId id = ins.insert(Constants.OBJ_TREE, new byte[] {});
ins.flush();
return id;
}
}
