Java tutorial
// 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 java.nio.charset.StandardCharsets.UTF_8; import com.google.gerrit.reviewdb.client.RefNames; import com.google.gerrit.server.GerritPersonIdent; import com.google.gerrit.server.config.GerritServerConfig; import com.google.inject.Inject; import org.eclipse.jgit.diff.Sequence; import org.eclipse.jgit.dircache.DirCache; import org.eclipse.jgit.dircache.DirCacheBuilder; import org.eclipse.jgit.dircache.DirCacheEntry; import org.eclipse.jgit.lib.CommitBuilder; 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.PersonIdent; import org.eclipse.jgit.lib.Ref; import org.eclipse.jgit.lib.RefUpdate; import org.eclipse.jgit.lib.Repository; import org.eclipse.jgit.merge.MergeFormatter; import org.eclipse.jgit.merge.MergeResult; 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; import org.eclipse.jgit.util.TemporaryBuffer; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.IOException; import java.io.InputStream; import java.util.HashMap; import java.util.Map; public class AutoMerger { private static final Logger log = LoggerFactory.getLogger(AutoMerger.class); private final PersonIdent gerritIdent; private final boolean save; @Inject AutoMerger(@GerritServerConfig Config cfg, @GerritPersonIdent PersonIdent gerritIdent) { save = cfg.getBoolean("change", null, "cacheAutomerge", true); this.gerritIdent = gerritIdent; } /** * Perform an auto-merge of the parents of the given merge commit. * * @return auto-merge commit or {@code null} if an auto-merge commit * couldn't be created. Headers of the returned RevCommit are parsed. */ public RevCommit merge(Repository repo, RevWalk rw, final ObjectInserter ins, RevCommit merge, ThreeWayMergeStrategy mergeStrategy) throws IOException { rw.parseHeaders(merge); String hash = merge.name(); String refName = RefNames.REFS_CACHE_AUTOMERGE + hash.substring(0, 2) + "/" + hash.substring(2); 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, ins, refName, obj, merge); } ResolveMerger m = (ResolveMerger) mergeStrategy.newMerger(repo, true); DirCache dc = DirCache.newInCore(); m.setDirCache(dc); m.setObjectInserter(new ObjectInserter.Filter() { @Override protected ObjectInserter delegate() { return ins; } @Override public void flush() { } @Override public void close() { } }); boolean couldMerge; try { couldMerge = m.merge(merge.getParents()); } catch (IOException e) { // It is not safe to continue further down in this method as throwing // an exception most likely means that the merge tree was not created // and m.getMergeResults() is empty. This would mean that all paths are // unmerged and Gerrit UI would show all paths in the patch list. log.warn("Error attempting automerge " + refName, e); return null; } ObjectId treeId; if (couldMerge) { treeId = m.getResultTreeId(); } else { RevCommit ours = merge.getParent(0); RevCommit theirs = merge.getParent(1); rw.parseBody(ours); rw.parseBody(theirs); String oursMsg = ours.getShortMessage(); String theirsMsg = theirs.getShortMessage(); String oursName = String.format("HEAD (%s %s)", ours.abbreviate(6).name(), oursMsg.substring(0, Math.min(oursMsg.length(), 60))); String theirsName = String.format("BRANCH (%s %s)", theirs.abbreviate(6).name(), theirsMsg.substring(0, Math.min(theirsMsg.length(), 60))); MergeFormatter fmt = new MergeFormatter(); Map<String, MergeResult<? extends Sequence>> r = m.getMergeResults(); Map<String, ObjectId> resolved = new HashMap<>(); for (Map.Entry<String, MergeResult<? extends Sequence>> entry : r.entrySet()) { MergeResult<? extends Sequence> p = entry.getValue(); try (TemporaryBuffer buf = new TemporaryBuffer.LocalFile(null, 10 * 1024 * 1024)) { fmt.formatMerge(buf, p, "BASE", oursName, theirsName, UTF_8.name()); buf.close(); try (InputStream in = buf.openInputStream()) { resolved.put(entry.getKey(), ins.insert(Constants.OBJ_BLOB, buf.length(), in)); } } } DirCacheBuilder builder = dc.builder(); int cnt = dc.getEntryCount(); for (int i = 0; i < cnt;) { DirCacheEntry entry = dc.getEntry(i); if (entry.getStage() == 0) { builder.add(entry); i++; continue; } int next = dc.nextEntry(i); String path = entry.getPathString(); DirCacheEntry res = new DirCacheEntry(path); if (resolved.containsKey(path)) { // For a file with content merge conflict that we produced a result // above on, collapse the file down to a single stage 0 with just // the blob content, and a randomly selected mode (the lowest stage, // which should be the merge base, or ours). res.setFileMode(entry.getFileMode()); res.setObjectId(resolved.get(path)); } else if (next == i + 1) { // If there is exactly one stage present, shouldn't be a conflict... res.setFileMode(entry.getFileMode()); res.setObjectId(entry.getObjectId()); } else if (next == i + 2) { // Two stages suggests a delete/modify conflict. Pick the higher // stage as the automatic result. entry = dc.getEntry(i + 1); res.setFileMode(entry.getFileMode()); res.setObjectId(entry.getObjectId()); } else { // 3 stage conflict, no resolve above // Punt on the 3-stage conflict and show the base, for now. res.setFileMode(entry.getFileMode()); res.setObjectId(entry.getObjectId()); } builder.add(res); i = next; } builder.finish(); treeId = dc.writeTree(ins); } ins.flush(); return commit(repo, rw, ins, refName, treeId, merge); } private RevCommit commit(Repository repo, RevWalk rw, 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); } ObjectId commitId; commitId = ins.insert(cb); if (save) { ins.flush(); RefUpdate ru = repo.updateRef(refName); ru.setNewObjectId(commitId); ru.disableRefLog(); ru.forceUpdate(); } return rw.parseCommit(commitId); } }