implement git rebase

scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMergeCommand.java

@@ -60,7 +60,8 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
   private static final Set<MergeStrategy> STRATEGIES = ImmutableSet.of(
     MergeStrategy.MERGE_COMMIT,
     MergeStrategy.FAST_FORWARD_IF_POSSIBLE,
-    MergeStrategy.SQUASH
+    MergeStrategy.SQUASH,
+    MergeStrategy.REBASE
   );
 
   @Inject
@@ -94,6 +95,9 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
       case MERGE_COMMIT:
         return inClone(clone -> new GitMergeCommit(clone, request, context, repository), workingCopyFactory, request.getTargetBranch());
 
+      case REBASE:
+        return inClone(clone -> new GitMergeRebase(clone, request, context, repository), workingCopyFactory, request.getTargetBranch());
+
       default:
         throw new MergeStrategyNotSupportedException(repository, request.getMergeStrategy());
     }

scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMergeRebase.java

@@ -0,0 +1,97 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package sonia.scm.repository.spi;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.MergeCommand;
+import org.eclipse.jgit.api.RebaseResult;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.lib.ObjectId;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import sonia.scm.repository.InternalRepositoryException;
+import sonia.scm.repository.Repository;
+import sonia.scm.repository.api.MergeCommandResult;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Optional;
+
+public class GitMergeRebase extends GitMergeStrategy {
+
+  private static final Logger logger = LoggerFactory.getLogger(GitMergeRebase.class);
+
+  private final MergeCommandRequest request;
+
+  GitMergeRebase(Git clone, MergeCommandRequest request, GitContext context, Repository repository) {
+    super(clone, request, context, repository);
+    this.request = request;
+  }
+
+  @Override
+  MergeCommandResult run() throws IOException {
+    RebaseResult result;
+    String branchToMerge = request.getBranchToMerge();
+    String targetBranch = request.getTargetBranch();
+    try {
+      checkOutBranch(branchToMerge);
+      result =
+        getClone()
+          .rebase()
+          .setUpstream(targetBranch)
+          .call();
+    } catch (GitAPIException e) {
+      throw new InternalRepositoryException(getContext().getRepository(), "could not merge branch " + branchToMerge + " into " + targetBranch, e);
+    }
+
+    if (result.getStatus().isSuccessful()) {
+      return fastForwardTargetBranch(branchToMerge, targetBranch, result);
+    } else {
+      logger.info("could not rebase branch {} into {} with rebase status '{}' due to ...", branchToMerge, targetBranch, result.getStatus());
+      logger.info("... conflicts: {}", result.getConflicts());
+      logger.info("... failing paths: {}", result.getFailingPaths());
+      logger.info("... message: {}", result);
+      return MergeCommandResult.failure(branchToMerge, targetBranch, Optional.ofNullable(result.getConflicts()).orElse(Collections.singletonList("UNKNOWN")));
+    }
+  }
+
+  private MergeCommandResult fastForwardTargetBranch(String branchToMerge, String targetBranch, RebaseResult result) throws IOException {
+    try {
+      getClone().checkout().setName(targetBranch).call();
+      ObjectId sourceRevision = resolveRevision(branchToMerge);
+      getClone()
+        .merge()
+        .setFastForward(MergeCommand.FastForwardMode.FF_ONLY)
+        .setCommit(false) // we want to set the author manually
+        .include(branchToMerge, sourceRevision)
+        .call();
+      push();
+      return MergeCommandResult.success(getTargetRevision().name(), branchToMerge, sourceRevision.name());
+    } catch (GitAPIException e) {
+      return MergeCommandResult.failure(branchToMerge, targetBranch, result.getConflicts());
+    }
+
+  }
+}