| // Copyright (C) 2016 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 static com.google.common.base.Preconditions.checkArgument; |
| |
| import com.google.common.base.Throwables; |
| import com.google.gerrit.common.Nullable; |
| import com.google.gerrit.common.UsedAt; |
| import com.google.gerrit.entities.RefNames; |
| import com.google.gerrit.git.LockFailureException; |
| import com.google.gerrit.server.GerritPersonIdent; |
| import com.google.gerrit.server.config.GerritServerConfig; |
| import com.google.gerrit.server.git.InMemoryInserter; |
| import com.google.gerrit.server.git.MergeUtil; |
| import com.google.gerrit.server.update.RetryHelper; |
| import com.google.gerrit.server.update.RetryableAction.ActionType; |
| import com.google.inject.Inject; |
| import java.io.IOException; |
| import org.eclipse.jgit.dircache.DirCache; |
| import org.eclipse.jgit.lib.CommitBuilder; |
| import org.eclipse.jgit.lib.Config; |
| import org.eclipse.jgit.lib.ObjectId; |
| import org.eclipse.jgit.lib.ObjectInserter; |
| import org.eclipse.jgit.lib.ObjectReader; |
| import org.eclipse.jgit.lib.PersonIdent; |
| import org.eclipse.jgit.lib.Ref; |
| import org.eclipse.jgit.lib.RefUpdate; |
| import org.eclipse.jgit.lib.Repository; |
| import org.eclipse.jgit.merge.ResolveMerger; |
| import org.eclipse.jgit.merge.ThreeWayMergeStrategy; |
| import org.eclipse.jgit.revwalk.RevCommit; |
| import org.eclipse.jgit.revwalk.RevObject; |
| import org.eclipse.jgit.revwalk.RevWalk; |
| |
| /** |
| * Utility class for creating an auto-merge commit of a merge commit. |
| * |
| * <p>An auto-merge commit is the result of merging the 2 parents of a merge commit automatically. |
| * If there are conflicts the auto-merge commit contains Git conflict markers that indicate these |
| * conflicts. |
| * |
| * <p>Creating auto-merge commits for octopus merges (merge commits with more than 2 parents) is not |
| * supported. In this case the auto-merge is created between the first 2 parent commits. |
| * |
| * <p>All created auto-merge commits are stored in the repository of their merge commit as {@code |
| * refs/cache-automerge/} branches. These branches serve: |
| * |
| * <ul> |
| * <li>as a cache so that the each auto-merge gets computed only once |
| * <li>as base for merge commits on which users can comment |
| * </ul> |
| * |
| * <p>The second point means that these commits are referenced from NoteDb. The consequence of this |
| * is that these refs should never be deleted. |
| */ |
| public class AutoMerger { |
| @UsedAt(UsedAt.Project.GOOGLE) |
| public static boolean cacheAutomerge(Config cfg) { |
| return cfg.getBoolean("change", null, "cacheAutomerge", true); |
| } |
| |
| private final RetryHelper retryHelper; |
| private final PersonIdent gerritIdent; |
| private final boolean save; |
| |
| @Inject |
| AutoMerger( |
| RetryHelper retryHelper, |
| @GerritServerConfig Config cfg, |
| @GerritPersonIdent PersonIdent gerritIdent) { |
| this.retryHelper = retryHelper; |
| save = cacheAutomerge(cfg); |
| this.gerritIdent = gerritIdent; |
| } |
| |
| /** |
| * Creates an auto-merge commit of the parents of the given merge commit. |
| * |
| * <p>In case of an exception the creation of the auto-merge commit is retried a few times. E.g. |
| * this allows the operation to succeed if a Git update fails due to a temporary issue. |
| * |
| * @return auto-merge commit. Headers of the returned RevCommit are parsed. |
| */ |
| public RevCommit merge( |
| Repository repo, |
| RevWalk rw, |
| ObjectInserter ins, |
| RevCommit merge, |
| ThreeWayMergeStrategy mergeStrategy) |
| throws IOException { |
| try { |
| return retryHelper |
| .action( |
| ActionType.GIT_UPDATE, |
| "createAutoMerge", |
| () -> createAutoMergeCommit(repo, rw, ins, merge, mergeStrategy)) |
| .call(); |
| } catch (Exception e) { |
| Throwables.throwIfUnchecked(e); |
| Throwables.throwIfInstanceOf(e, IOException.class); |
| throw new IllegalStateException(e); |
| } |
| } |
| |
| /** |
| * Creates an auto-merge commit of the parents of the given merge commit. |
| * |
| * @return auto-merge commit. Headers of the returned RevCommit are parsed. |
| */ |
| private RevCommit createAutoMergeCommit( |
| Repository repo, |
| RevWalk rw, |
| ObjectInserter ins, |
| RevCommit merge, |
| ThreeWayMergeStrategy mergeStrategy) |
| throws IOException { |
| checkArgument(rw.getObjectReader().getCreatedFromInserter() == ins); |
| |
| InMemoryInserter tmpIns = null; |
| if (ins instanceof InMemoryInserter) { |
| // Caller gave us an in-memory inserter, so ensure anything we write from |
| // this method is visible to them. |
| tmpIns = (InMemoryInserter) ins; |
| } else if (!save) { |
| // If we don't plan on saving results, use a fully in-memory inserter. |
| // Using just a non-flushing wrapper is not sufficient, since in |
| // particular DfsInserter might try to write to storage after exceeding an |
| // internal buffer size. |
| tmpIns = new InMemoryInserter(rw.getObjectReader()); |
| } |
| |
| rw.parseHeaders(merge); |
| String refName = RefNames.refsCacheAutomerge(merge.name()); |
| Ref ref = repo.getRefDatabase().exactRef(refName); |
| if (ref != null && ref.getObjectId() != null) { |
| RevObject obj = rw.parseAny(ref.getObjectId()); |
| if (obj instanceof RevCommit) { |
| return (RevCommit) obj; |
| } |
| return commit(repo, rw, tmpIns, ins, refName, obj, merge); |
| } |
| |
| ResolveMerger m = (ResolveMerger) mergeStrategy.newMerger(repo, true); |
| DirCache dc = DirCache.newInCore(); |
| m.setDirCache(dc); |
| m.setObjectInserter(tmpIns == null ? new NonFlushingWrapper(ins) : tmpIns); |
| |
| boolean couldMerge = m.merge(merge.getParents()); |
| |
| ObjectId treeId; |
| if (couldMerge) { |
| treeId = m.getResultTreeId(); |
| } else { |
| treeId = |
| MergeUtil.mergeWithConflicts( |
| rw, |
| ins, |
| dc, |
| "HEAD", |
| merge.getParent(0), |
| "BRANCH", |
| merge.getParent(1), |
| m.getMergeResults()); |
| } |
| |
| return commit(repo, rw, tmpIns, ins, refName, treeId, merge); |
| } |
| |
| private RevCommit commit( |
| Repository repo, |
| RevWalk rw, |
| @Nullable InMemoryInserter tmpIns, |
| ObjectInserter ins, |
| String refName, |
| ObjectId tree, |
| RevCommit merge) |
| throws IOException { |
| rw.parseHeaders(merge); |
| // For maximum stability, choose a single ident using the committer time of |
| // the input commit, using the server name and timezone. |
| PersonIdent ident = |
| new PersonIdent( |
| gerritIdent, merge.getCommitterIdent().getWhen(), gerritIdent.getTimeZone()); |
| CommitBuilder cb = new CommitBuilder(); |
| cb.setAuthor(ident); |
| cb.setCommitter(ident); |
| cb.setTreeId(tree); |
| cb.setMessage("Auto-merge of " + merge.name() + '\n'); |
| for (RevCommit p : merge.getParents()) { |
| cb.addParentId(p); |
| } |
| |
| if (!save) { |
| checkArgument(tmpIns != null); |
| try (ObjectReader tmpReader = tmpIns.newReader(); |
| RevWalk tmpRw = new RevWalk(tmpReader)) { |
| return tmpRw.parseCommit(tmpIns.insert(cb)); |
| } |
| } |
| |
| checkArgument(tmpIns == null); |
| checkArgument(!(ins instanceof InMemoryInserter)); |
| ObjectId commitId = ins.insert(cb); |
| ins.flush(); |
| |
| RefUpdate ru = repo.updateRef(refName); |
| ru.setNewObjectId(commitId); |
| ru.disableRefLog(); |
| switch (ru.forceUpdate()) { |
| case FAST_FORWARD: |
| case FORCED: |
| case NEW: |
| case NO_CHANGE: |
| return rw.parseCommit(commitId); |
| 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 static class NonFlushingWrapper extends ObjectInserter.Filter { |
| private final ObjectInserter ins; |
| |
| private NonFlushingWrapper(ObjectInserter ins) { |
| this.ins = ins; |
| } |
| |
| @Override |
| protected ObjectInserter delegate() { |
| return ins; |
| } |
| |
| @Override |
| public void flush() {} |
| |
| @Override |
| public void close() {} |
| } |
| } |