Extract the PatchListLoader.automerge into the new AutoMerger class

This is a preparation step for storing commits instead of just trees
under the refs/cache-automerge/. The main advantage now is that we
can inject additional dependencies into the AutoMerger.

Change-Id: Id0b7b14217de0260691f894d47f7909251df6ce1

gerrit-server/src/main/java/com/google/gerrit/server/index/change/AllChangesIndexer.java

@@ -39,7 +39,7 @@ import com.google.gerrit.server.git.MultiProgressMonitor.Task;
 import com.google.gerrit.server.index.IndexExecutor;
 import com.google.gerrit.server.index.SiteIndexer;
 import com.google.gerrit.server.notedb.ChangeNotes;
-import com.google.gerrit.server.patch.PatchListLoader;
+import com.google.gerrit.server.patch.AutoMerger;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gwtorm.server.SchemaFactory;
@@ -90,6 +90,7 @@ public class AllChangesIndexer
   private final ChangeNotes.Factory notesFactory;
   private final ProjectCache projectCache;
   private final ThreeWayMergeStrategy mergeStrategy;
+  private final AutoMerger autoMerger;
 
   @Inject
   AllChangesIndexer(SchemaFactory<ReviewDb> schemaFactory,
@@ -99,7 +100,8 @@ public class AllChangesIndexer
       ChangeIndexer.Factory indexerFactory,
       ChangeNotes.Factory notesFactory,
       @GerritServerConfig Config config,
-      ProjectCache projectCache) {
+      ProjectCache projectCache,
+      AutoMerger autoMerger) {
     this.schemaFactory = schemaFactory;
     this.changeDataFactory = changeDataFactory;
     this.repoManager = repoManager;
@@ -108,6 +110,7 @@ public class AllChangesIndexer
     this.notesFactory = notesFactory;
     this.projectCache = projectCache;
     this.mergeStrategy = MergeUtil.getMergeStrategy(config);
+    this.autoMerger = autoMerger;
   }
 
   @Override
@@ -236,6 +239,7 @@ public class AllChangesIndexer
           }
           new ProjectIndexer(indexer,
               mergeStrategy,
+              autoMerger,
               byId,
               repo,
               done,
@@ -257,6 +261,7 @@ public class AllChangesIndexer
   private static class ProjectIndexer implements Callable<Void> {
     private final ChangeIndexer indexer;
     private final ThreeWayMergeStrategy mergeStrategy;
+    private final AutoMerger autoMerger;
     private final Multimap<ObjectId, ChangeData> byId;
     private final ProgressMonitor done;
     private final ProgressMonitor failed;
@@ -266,6 +271,7 @@ public class AllChangesIndexer
 
     private ProjectIndexer(ChangeIndexer indexer,
         ThreeWayMergeStrategy mergeStrategy,
+        AutoMerger autoMerger,
         Multimap<ObjectId, ChangeData> changesByCommitId,
         Repository repo,
         ProgressMonitor done,
@@ -273,6 +279,7 @@ public class AllChangesIndexer
         PrintWriter verboseWriter) {
       this.indexer = indexer;
       this.mergeStrategy = mergeStrategy;
+      this.autoMerger = autoMerger;
       this.byId = changesByCommitId;
       this.repo = repo;
       this.done = done;
@@ -366,7 +373,7 @@ public class AllChangesIndexer
           walk.parseBody(a);
           return walk.parseTree(a.getTree());
         case 2:
-          return PatchListLoader.automerge(repo, walk, b, mergeStrategy);
+          return autoMerger.merge(repo, walk, b, mergeStrategy);
         default:
           return null;
       }

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

@@ -0,0 +1,189 @@
+// 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.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.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectInserter;
+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.RevTree;
+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);
+
+  @Inject
+  AutoMerger() {
+  }
+
+  public RevTree merge(Repository repo, RevWalk rw, 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) {
+      return rw.parseTree(ref.getObjectId());
+    }
+
+    ResolveMerger m = (ResolveMerger) mergeStrategy.newMerger(repo, true);
+    try (ObjectInserter ins = repo.newObjectInserter()) {
+      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();
+
+      RefUpdate update = repo.updateRef(refName);
+      update.setNewObjectId(treeId);
+      update.disableRefLog();
+      update.forceUpdate();
+
+      return rw.lookupTree(treeId);
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchListLoader.java

@@ -24,7 +24,6 @@ import com.google.common.collect.FluentIterable;
 import com.google.gerrit.extensions.client.DiffPreferencesInfo.Whitespace;
 import com.google.gerrit.reviewdb.client.Patch;
 import com.google.gerrit.reviewdb.client.Project;
-import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.server.config.ConfigUtil;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.git.GitRepositoryManager;
@@ -39,22 +38,13 @@ import org.eclipse.jgit.diff.EditList;
 import org.eclipse.jgit.diff.HistogramDiff;
 import org.eclipse.jgit.diff.RawText;
 import org.eclipse.jgit.diff.RawTextComparator;
-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.Config;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.FileMode;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.ObjectReader;
-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.patch.FileHeader;
 import org.eclipse.jgit.patch.FileHeader.PatchType;
@@ -63,18 +53,14 @@ import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.TreeWalk;
-import org.eclipse.jgit.util.TemporaryBuffer;
 import org.eclipse.jgit.util.io.DisabledOutputStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
-import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
@@ -94,6 +80,7 @@ public class PatchListLoader implements Callable<PatchList> {
   private final PatchListCache patchListCache;
   private final ThreeWayMergeStrategy mergeStrategy;
   private final ExecutorService diffExecutor;
+  private final AutoMerger autoMerger;
   private final PatchListKey key;
   private final Project.NameKey project;
   private final long timeoutMillis;
@@ -104,12 +91,14 @@ public class PatchListLoader implements Callable<PatchList> {
       PatchListCache plc,
       @GerritServerConfig Config cfg,
       @DiffExecutor ExecutorService de,
+      AutoMerger am,
       @Assisted PatchListKey k,
       @Assisted Project.NameKey p) {
     repoManager = mgr;
     patchListCache = plc;
     mergeStrategy = MergeUtil.getMergeStrategy(cfg);
     diffExecutor = de;
+    autoMerger = am;
     key = k;
     project = p;
     lock = new Object();
@@ -344,146 +333,13 @@ public class PatchListLoader implements Callable<PatchList> {
         return r;
       }
       case 2:
-        return automerge(repo, rw, b, mergeStrategy);
+        return autoMerger.merge(repo, rw, b, mergeStrategy);
       default:
         // TODO(sop) handle an octopus merge.
         return null;
     }
   }
 
-  public static RevTree automerge(Repository repo, RevWalk rw, RevCommit b,
-      ThreeWayMergeStrategy mergeStrategy) throws IOException {
-    String hash = b.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) {
-      return rw.parseTree(ref.getObjectId());
-    }
-
-    ResolveMerger m = (ResolveMerger) mergeStrategy.newMerger(repo, true);
-    try (ObjectInserter ins = repo.newObjectInserter()) {
-      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(b.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 = b.getParent(0);
-        RevCommit theirs = b.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();
-
-      RefUpdate update = repo.updateRef(refName);
-      update.setNewObjectId(treeId);
-      update.disableRefLog();
-      update.forceUpdate();
-
-      return rw.lookupTree(treeId);
-    }
-  }
-
   private static ObjectId emptyTree(final Repository repo) throws IOException {
     try (ObjectInserter oi = repo.newObjectInserter()) {
       ObjectId id = oi.insert(Constants.OBJ_TREE, new byte[] {});