private ObjectId mergeCommits()

in git-server/src/main/java/jetbrains/buildServer/buildTriggers/vcs/git/GitMergeSupport.java [172:239]
61 lines of code
9 McCabe index (conditional complexity)

  private ObjectId mergeCommits(@NotNull GitVcsRoot gitRoot,
                                @NotNull Repository db,
                                @NotNull RevCommit srcCommit,
                                @NotNull RevCommit dstCommit,
                                @NotNull String message,
                                @NotNull MergeOptions options) throws IOException, MergeFailedException {
    if (!alwaysCreateMergeCommit(options)) {
      RevWalk walk = new RevWalk(db);
      try {
        if (walk.isMergedInto(walk.parseCommit(dstCommit), walk.parseCommit(srcCommit))) {
          LOG.debug("Commit " + srcCommit.name() + " already merged into " + dstCommit + ", skip the merge");
          return srcCommit;
        }
      } finally {
        walk.close();
      }
    }

    if (tryRebase(options)) {
      LOG.debug("Run rebase, root " + gitRoot + ", revision " + srcCommit.name() + ", destination " + dstCommit.name());
      try {
        return rebase(gitRoot, db, srcCommit, dstCommit);
      } catch (MergeFailedException e) {
        if (enforceLinearHistory(options)) {
          LOG.debug("Rebase failed, root " + gitRoot + ", revision " + srcCommit.name() + ", destination " + dstCommit.name(), e);
          throw e;
        }
      } catch (IOException e) {
        if (enforceLinearHistory(options)) {
          LOG.debug("Rebase failed, root " + gitRoot + ", revision " + srcCommit.name() + ", destination " + dstCommit.name(), e);
          throw e;
        }
      }
    }

    ResolveMerger merger = (ResolveMerger) MergeStrategy.RECURSIVE.newMerger(db, true);
    boolean mergeSuccessful = merger.merge(dstCommit, srcCommit);
    if (!mergeSuccessful) {
      List<String> conflicts = merger.getUnmergedPaths();
      Collections.sort(conflicts);
      LOG.debug("Merge failed with conflicts, root " + gitRoot + ", revision " + srcCommit.name() + ", destination " + dstCommit.name() +
                ", conflicts " + conflicts);
      throw new MergeFailedException(conflicts);
    }

    ObjectInserter inserter = db.newObjectInserter();
    DirCache dc = DirCache.newInCore();
    DirCacheBuilder dcb = dc.builder();

    dcb.addTree(new byte[]{}, 0, db.getObjectDatabase().newReader(), merger.getResultTreeId());
    inserter.flush();
    dcb.finish();

    ObjectId writtenTreeId = dc.writeTree(inserter);

    CommitBuilder commitBuilder = new CommitBuilder();
    final PersonIdent tagger = PersonIdentFactory.getTagger(gitRoot, db);
    commitBuilder.setCommitter(tagger);
    commitBuilder.setAuthor(tagger);
    commitBuilder.setMessage(message);
    commitBuilder.addParentId(dstCommit);
    commitBuilder.addParentId(srcCommit);
    commitBuilder.setTreeId(writtenTreeId);

    ObjectId commitId = inserter.insert(commitBuilder);
    inserter.flush();
    return commitId;
  }