1 files changed, 127 insertions, 0 deletions
diff --git a/java/com/google/gerrit/server/restapi/project/CheckMergeability.java b/java/com/google/gerrit/server/restapi/project/CheckMergeability.java
new file mode 100644
index 0000000000..de2ac6458d
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/project/CheckMergeability.java
@@ -0,0 +1,127 @@
+// 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.restapi.project;
+
+import com.google.gerrit.extensions.client.SubmitType;
+import com.google.gerrit.extensions.common.MergeableInfo;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.git.InMemoryInserter;
+import com.google.gerrit.server.git.MergeUtil;
+import com.google.gerrit.server.project.BranchResource;
+import com.google.inject.Inject;
+import java.io.IOException;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.merge.Merger;
+import org.eclipse.jgit.merge.ResolveMerger;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.kohsuke.args4j.Option;
+
+/** Check the mergeability at current branch for a git object references expression. */
+public class CheckMergeability implements RestReadView<BranchResource> {
+  private String source;
+  private String strategy;
+  private SubmitType submitType;
+
+  @Option(
+      name = "--source",
+      metaVar = "COMMIT",
+      usage =
+          "the source reference to merge, which could be any git object "
+              + "references expression, refer to "
+              + "org.eclipse.jgit.lib.Repository#resolve(String)",
+      required = true)
+  public void setSource(String source) {
+    this.source = source;
+  }
+
+  @Option(
+      name = "--strategy",
+      metaVar = "STRATEGY",
+      usage = "name of the merge strategy, refer to org.eclipse.jgit.merge.MergeStrategy")
+  public void setStrategy(String strategy) {
+    this.strategy = strategy;
+  }
+
+  private final GitRepositoryManager gitManager;
+  private final CommitsCollection commits;
+
+  @Inject
+  CheckMergeability(
+      GitRepositoryManager gitManager, CommitsCollection commits, @GerritServerConfig Config cfg) {
+    this.gitManager = gitManager;
+    this.commits = commits;
+    this.strategy = MergeUtil.getMergeStrategy(cfg).getName();
+    this.submitType = cfg.getEnum("project", null, "submitType", SubmitType.MERGE_IF_NECESSARY);
+  }
+
+  @Override
+  public MergeableInfo apply(BranchResource resource)
+      throws IOException, BadRequestException, ResourceNotFoundException {
+    if (!(submitType.equals(SubmitType.MERGE_ALWAYS)
+        || submitType.equals(SubmitType.MERGE_IF_NECESSARY))) {
+      throw new BadRequestException("Submit type: " + submitType + " is not supported");
+    }
+
+    MergeableInfo result = new MergeableInfo();
+    result.submitType = submitType;
+    result.strategy = strategy;
+    try (Repository git = gitManager.openRepository(resource.getNameKey());
+        RevWalk rw = new RevWalk(git);
+        ObjectInserter inserter = new InMemoryInserter(git)) {
+      Merger m = MergeUtil.newMerger(inserter, git.getConfig(), strategy);
+
+      Ref destRef = git.getRefDatabase().exactRef(resource.getRef());
+      if (destRef == null) {
+        throw new ResourceNotFoundException(resource.getRef());
+      }
+
+      RevCommit targetCommit = rw.parseCommit(destRef.getObjectId());
+      RevCommit sourceCommit = MergeUtil.resolveCommit(git, rw, source);
+
+      if (!commits.canRead(resource.getProjectState(), git, sourceCommit)) {
+        throw new BadRequestException("do not have read permission for: " + source);
+      }
+
+      if (rw.isMergedInto(sourceCommit, targetCommit)) {
+        result.mergeable = true;
+        result.commitMerged = true;
+        result.contentMerged = true;
+        return result;
+      }
+
+      if (m.merge(false, targetCommit, sourceCommit)) {
+        result.mergeable = true;
+        result.commitMerged = false;
+        result.contentMerged = m.getResultTreeId().equals(targetCommit.getTree());
+      } else {
+        result.mergeable = false;
+        if (m instanceof ResolveMerger) {
+          result.conflicts = ((ResolveMerger) m).getUnmergedPaths();
+        }
+      }
+    } catch (IllegalArgumentException e) {
+      throw new BadRequestException(e.getMessage());
+    }
+    return result;
+  }
+}