gerrit-server/src/main/java/com/google/gerrit/server/patch/AutoMerger.java - gerrit - Git at Google

 // 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 static java.nio.charset.StandardCharsets.UTF_8;

 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.server.GerritPersonIdent;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.git.InMemoryInserter;
 import com.google.inject.Inject;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.HashMap;
 import java.util.Map;
 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.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.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;

 public class AutoMerger {
   private static final Logger log = LoggerFactory.getLogger(AutoMerger.class);

   public static boolean cacheAutomerge(Config cfg) {
     return cfg.getBoolean("change", null, "cacheAutomerge", true);
   }

   private final PersonIdent gerritIdent;
   private final boolean save;

   @Inject
   AutoMerger(@GerritServerConfig Config cfg, @GerritPersonIdent PersonIdent gerritIdent) {
     save = cacheAutomerge(cfg);
     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,
       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;
     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);
     }

     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();
     ru.forceUpdate();
     return rw.parseCommit(commitId);
   }

   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() {}
   }
 }
	// 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 static java.nio.charset.StandardCharsets.UTF_8;

	import com.google.gerrit.common.Nullable;
	import com.google.gerrit.reviewdb.client.RefNames;
	import com.google.gerrit.server.GerritPersonIdent;
	import com.google.gerrit.server.config.GerritServerConfig;
	import com.google.gerrit.server.git.InMemoryInserter;
	import com.google.inject.Inject;
	import java.io.IOException;
	import java.io.InputStream;
	import java.util.HashMap;
	import java.util.Map;
	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.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.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;

	public class AutoMerger {
	private static final Logger log = LoggerFactory.getLogger(AutoMerger.class);

	public static boolean cacheAutomerge(Config cfg) {
	return cfg.getBoolean("change", null, "cacheAutomerge", true);
	}

	private final PersonIdent gerritIdent;
	private final boolean save;

	@Inject
	AutoMerger(@GerritServerConfig Config cfg, @GerritPersonIdent PersonIdent gerritIdent) {
	save = cacheAutomerge(cfg);
	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,
	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;
	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);
	}

	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();
	ru.forceUpdate();
	return rw.parseCommit(commitId);
	}

	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() {}
	}
	}