Line data    Source code

       1             : // Copyright (C) 2020 The Android Open Source Project
       2             : //
       3             : // Licensed under the Apache License, Version 2.0 (the "License");
       4             : // you may not use this file except in compliance with the License.
       5             : // You may obtain a copy of the License at
       6             : //
       7             : // http://www.apache.org/licenses/LICENSE-2.0
       8             : //
       9             : // Unless required by applicable law or agreed to in writing, software
      10             : // distributed under the License is distributed on an "AS IS" BASIS,
      11             : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      12             : // See the License for the specific language governing permissions and
      13             : // limitations under the License.
      14             : 
      15             : package com.google.gerrit.server.patch;
      16             : 
      17             : import com.google.gerrit.common.Nullable;
      18             : import com.google.gerrit.entities.Project;
      19             : import com.google.gerrit.entities.RefNames;
      20             : import com.google.gerrit.server.config.GerritServerConfig;
      21             : import com.google.gerrit.server.git.GitRepositoryManager;
      22             : import com.google.gerrit.server.git.InMemoryInserter;
      23             : import com.google.gerrit.server.update.RepoView;
      24             : import com.google.inject.Inject;
      25             : import com.google.inject.Singleton;
      26             : import java.io.IOException;
      27             : import java.util.Optional;
      28             : import org.eclipse.jgit.lib.Config;
      29             : import org.eclipse.jgit.lib.Constants;
      30             : import org.eclipse.jgit.lib.ObjectId;
      31             : import org.eclipse.jgit.lib.ObjectInserter;
      32             : import org.eclipse.jgit.lib.ObjectReader;
      33             : import org.eclipse.jgit.lib.Repository;
      34             : import org.eclipse.jgit.revwalk.RevCommit;
      35             : import org.eclipse.jgit.revwalk.RevObject;
      36             : import org.eclipse.jgit.revwalk.RevWalk;
      37             : 
      38             : /** A utility class for computing the base commit / parent for a specific patchset commit. */
      39             : @Singleton
      40             : class BaseCommitUtil {
      41             :   private final AutoMerger autoMerger;
      42             :   private final GitRepositoryManager repoManager;
      43             : 
      44             :   /** If true, auto-merge results are stored in the repository. */
      45             :   private final boolean saveAutomerge;
      46             : 
      47             :   @Inject
      48         152 :   BaseCommitUtil(AutoMerger am, @GerritServerConfig Config cfg, GitRepositoryManager repoManager) {
      49         152 :     this.autoMerger = am;
      50         152 :     this.saveAutomerge = AutoMerger.cacheAutomerge(cfg);
      51         152 :     this.repoManager = repoManager;
      52         152 :   }
      53             : 
      54             :   RevObject getBaseCommit(Project.NameKey project, ObjectId newCommit, @Nullable Integer parentNum)
      55             :       throws IOException {
      56         100 :     try (Repository repo = repoManager.openRepository(project);
      57         100 :         ObjectInserter ins = newInserter(repo);
      58         100 :         ObjectReader reader = ins.newReader();
      59         100 :         RevWalk rw = new RevWalk(reader)) {
      60         100 :       return getParentCommit(repo, ins, rw, parentNum, newCommit);
      61             :     }
      62             :   }
      63             : 
      64             :   /**
      65             :    * Returns the number of parent commits of the commit represented by the commitId parameter.
      66             :    *
      67             :    * @param project a specific git repository.
      68             :    * @param commitId 20 bytes commitId SHA-1 hash.
      69             :    * @return an integer representing the number of parents of the designated commit.
      70             :    */
      71             :   int getNumParents(Project.NameKey project, ObjectId commitId) throws IOException {
      72         104 :     try (Repository repo = repoManager.openRepository(project);
      73         104 :         ObjectInserter ins = repo.newObjectInserter();
      74         104 :         ObjectReader reader = ins.newReader();
      75         104 :         RevWalk rw = new RevWalk(reader)) {
      76         104 :       RevCommit current = rw.parseCommit(commitId);
      77         104 :       return current.getParentCount();
      78             :     }
      79             :   }
      80             : 
      81             :   /**
      82             :    * Returns the parent commit Object of the commit represented by the commitId parameter.
      83             :    *
      84             :    * @param repo a git repository.
      85             :    * @param ins a git object inserter in the database.
      86             :    * @param rw a {@link RevWalk} object of the repository.
      87             :    * @param parentNum used to identify the parent number for merge commits. If parentNum is null and
      88             :    *     {@code commitId} has two parents, the auto-merge commit will be returned. If {@code
      89             :    *     commitId} has a single parent, it will be returned.
      90             :    * @param commitId 20 bytes commitId SHA-1 hash.
      91             :    * @return Returns the parent commit of the commit represented by the commitId parameter. Note
      92             :    *     that auto-merge is not supported for commits having more than two parents.
      93             :    */
      94             :   @Nullable
      95             :   RevObject getParentCommit(
      96             :       Repository repo,
      97             :       ObjectInserter ins,
      98             :       RevWalk rw,
      99             :       @Nullable Integer parentNum,
     100             :       ObjectId commitId)
     101             :       throws IOException {
     102         100 :     RevCommit current = rw.parseCommit(commitId);
     103         100 :     switch (current.getParentCount()) {
     104             :       case 0:
     105           0 :         return rw.parseAny(emptyTree(ins));
     106             :       case 1:
     107         100 :         return current.getParent(0);
     108             :       default:
     109          31 :         if (parentNum != null) {
     110          10 :           RevCommit r = current.getParent(parentNum - 1);
     111          10 :           rw.parseBody(r);
     112          10 :           return r;
     113             :         }
     114             :         // Only support auto-merge for 2 parents, not octopus merges
     115          31 :         if (current.getParentCount() == 2) {
     116          31 :           if (!saveAutomerge) {
     117           0 :             throw new IOException(
     118             :                 "diff against auto-merge commits is only supported if 'change.cacheAutomerge' config is set to true.");
     119             :           }
     120             :           // TODO(ghareeb): Avoid persisting auto-merge commits.
     121          31 :           return getAutoMergeFromGitOrCreate(repo, ins, rw, current);
     122             :         }
     123           0 :         return null;
     124             :     }
     125             :   }
     126             : 
     127             :   /**
     128             :    * Gets the auto-merge commit from git if it already exists. If not, the auto-merge is created,
     129             :    * persisted in git and the cache-automerge ref is updated for the merge commit.
     130             :    *
     131             :    * @return the auto-merge {@link RevCommit}
     132             :    */
     133             :   private RevCommit getAutoMergeFromGitOrCreate(
     134             :       Repository repo, ObjectInserter ins, RevWalk rw, RevCommit mergeCommit) throws IOException {
     135          31 :     String refName = RefNames.refsCacheAutomerge(mergeCommit.name());
     136          31 :     Optional<RevCommit> autoMergeCommit = autoMerger.lookupCommit(repo, rw, refName);
     137          31 :     if (autoMergeCommit.isPresent()) {
     138          30 :       return autoMergeCommit.get();
     139             :     }
     140           1 :     ObjectId autoMergeId =
     141           1 :         autoMerger.createAutoMergeCommit(new RepoView(repo, rw, ins), rw, ins, mergeCommit);
     142           1 :     ins.flush();
     143           1 :     return rw.parseCommit(autoMergeId);
     144             :   }
     145             : 
     146             :   private ObjectInserter newInserter(Repository repo) {
     147         100 :     return saveAutomerge ? repo.newObjectInserter() : new InMemoryInserter(repo);
     148             :   }
     149             : 
     150             :   private static ObjectId emptyTree(ObjectInserter ins) throws IOException {
     151           0 :     ObjectId id = ins.insert(Constants.OBJ_TREE, new byte[] {});
     152           0 :     ins.flush();
     153           0 :     return id;
     154             :   }
     155             : }