Merge with 2.0.0-m3

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

@@ -178,19 +178,28 @@ class AbstractGitCommand
   }
 
   ObjectId resolveRevisionOrThrowNotFound(Repository repository, String revision) throws IOException {
+    sonia.scm.repository.Repository scmRepository = context.getRepository();
+    return resolveRevisionOrThrowNotFound(repository, revision, scmRepository);
+  }
+
+  static ObjectId resolveRevisionOrThrowNotFound(Repository repository, String revision, sonia.scm.repository.Repository scmRepository) throws IOException {
     ObjectId resolved = repository.resolve(revision);
     if (resolved == null) {
-      throw notFound(entity("Revision", revision).in(context.getRepository()));
+      throw notFound(entity("Revision", revision).in(scmRepository));
     } else {
       return resolved;
     }
   }
 
-  abstract class GitCloneWorker<R> {
+  abstract static class GitCloneWorker<R> {
     private final Git clone;
+    private final GitContext context;
+    private final sonia.scm.repository.Repository repository;
 
-    GitCloneWorker(Git clone) {
+    GitCloneWorker(Git clone, GitContext context, sonia.scm.repository.Repository repository) {
       this.clone = clone;
+      this.context = context;
+      this.repository = repository;
     }
 
     abstract R run() throws IOException;
@@ -199,6 +208,10 @@ class AbstractGitCommand
       return clone;
     }
 
+    GitContext getContext() {
+      return context;
+    }
+
     void checkOutBranch(String branchName) throws IOException {
       try {
         clone.checkout().setName(branchName).call();
@@ -225,7 +238,7 @@ class AbstractGitCommand
     ObjectId resolveRevision(String revision) throws IOException {
       ObjectId resolved = clone.getRepository().resolve(revision);
       if (resolved == null) {
-        return resolveRevisionOrThrowNotFound(clone.getRepository(), "origin/" + revision);
+        return resolveRevisionOrThrowNotFound(clone.getRepository(), "origin/" + revision, context.getRepository());
       } else {
         return resolved;
       }

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

@@ -0,0 +1,36 @@
+package sonia.scm.repository.spi;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.MergeCommand;
+import org.eclipse.jgit.api.MergeResult;
+import sonia.scm.repository.Repository;
+import sonia.scm.repository.api.MergeCommandResult;
+
+import java.io.IOException;
+
+class GitFastForwardIfPossible extends GitMergeStrategy {
+
+  private GitMergeStrategy fallbackMerge;
+
+  GitFastForwardIfPossible(Git clone, MergeCommandRequest request, GitContext context, Repository repository) {
+    super(clone, request, context, repository);
+    fallbackMerge = new GitMergeCommit(clone, request, context, repository);
+  }
+
+  @Override
+  MergeCommandResult run() throws IOException {
+    MergeResult fastForwardResult = mergeWithFastForwardOnlyMode();
+    if (fastForwardResult.getMergeStatus().isSuccessful()) {
+      push();
+      return MergeCommandResult.success();
+    } else {
+      return fallbackMerge.run();
+    }
+  }
+
+  private MergeResult mergeWithFastForwardOnlyMode() throws IOException {
+    MergeCommand mergeCommand = getClone().merge();
+    mergeCommand.setFastForward(MergeCommand.FastForwardMode.FF_ONLY);
+    return doMergeInClone(mergeCommand);
+  }
+}

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

@@ -1,41 +1,39 @@
 package sonia.scm.repository.spi;
 
-import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableSet;
 import org.eclipse.jgit.api.Git;
-import org.eclipse.jgit.api.MergeCommand.FastForwardMode;
 import org.eclipse.jgit.api.MergeResult;
 import org.eclipse.jgit.api.Status;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.merge.MergeStrategy;
 import org.eclipse.jgit.merge.ResolveMerger;
 import org.eclipse.jgit.treewalk.CanonicalTreeParser;
 import org.eclipse.jgit.treewalk.filter.PathFilter;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 import sonia.scm.repository.GitWorkdirFactory;
 import sonia.scm.repository.InternalRepositoryException;
-import sonia.scm.repository.Person;
 import sonia.scm.repository.api.MergeCommandResult;
 import sonia.scm.repository.api.MergeDryRunCommandResult;
+import sonia.scm.repository.api.MergeStrategy;
+import sonia.scm.repository.api.MergeStrategyNotSupportedException;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.text.MessageFormat;
+import java.util.Set;
+
+import static org.eclipse.jgit.merge.MergeStrategy.RECURSIVE;
 
 public class GitMergeCommand extends AbstractGitCommand implements MergeCommand {
 
-  private static final Logger logger = LoggerFactory.getLogger(GitMergeCommand.class);
-
-  private static final String MERGE_COMMIT_MESSAGE_TEMPLATE = String.join("\n",
-    "Merge of branch {0} into {1}",
-    "",
-    "Automatic merge by SCM-Manager.");
-
   private final GitWorkdirFactory workdirFactory;
 
+  private static final Set<MergeStrategy> STRATEGIES = ImmutableSet.of(
+    MergeStrategy.MERGE_COMMIT,
+    MergeStrategy.FAST_FORWARD_IF_POSSIBLE,
+    MergeStrategy.SQUASH
+  );
+
   GitMergeCommand(GitContext context, sonia.scm.repository.Repository repository, GitWorkdirFactory workdirFactory) {
     super(context, repository);
     this.workdirFactory = workdirFactory;
@@ -43,14 +41,36 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
 
   @Override
   public MergeCommandResult merge(MergeCommandRequest request) {
-    return inClone(clone -> new MergeWorker(clone, request), workdirFactory, request.getTargetBranch());
+    return mergeWithStrategy(request);
+  }
+
+  @Override
+  public MergeConflictResult computeConflicts(MergeCommandRequest request) {
+    WorkingCopyCloser closer = new WorkingCopyCloser();
+    return inClone(git -> new ConflictWorker(git, request, closer), workdirFactory, request.getTargetBranch());
+  }
+
+  private MergeCommandResult mergeWithStrategy(MergeCommandRequest request) {
+    switch(request.getMergeStrategy()) {
+      case SQUASH:
+        return inClone(clone -> new GitMergeWithSquash(clone, request, context, repository), workdirFactory, request.getTargetBranch());
+
+      case FAST_FORWARD_IF_POSSIBLE:
+        return inClone(clone -> new GitFastForwardIfPossible(clone, request, context, repository), workdirFactory, request.getTargetBranch());
+
+      case MERGE_COMMIT:
+        return inClone(clone -> new GitMergeCommit(clone, request, context, repository), workdirFactory, request.getTargetBranch());
+
+      default:
+        throw new MergeStrategyNotSupportedException(repository, request.getMergeStrategy());
+    }
   }
 
   @Override
   public MergeDryRunCommandResult dryRun(MergeCommandRequest request) {
     try {
       Repository repository = context.open();
-      ResolveMerger merger = (ResolveMerger) MergeStrategy.RECURSIVE.newMerger(repository, true);
+      ResolveMerger merger = (ResolveMerger) RECURSIVE.newMerger(repository, true);
       return new MergeDryRunCommandResult(
         merger.merge(
           resolveRevisionOrThrowNotFound(repository, request.getBranchToMerge()),
@@ -61,70 +81,13 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
   }
 
   @Override
-  public MergeConflictResult computeConflicts(MergeCommandRequest request) {
-    WorkingCopyCloser closer = new WorkingCopyCloser();
-    return inClone(git -> new ConflictWorker(git, request, closer), workdirFactory, request.getTargetBranch());
+  public boolean isSupported(MergeStrategy strategy) {
+    return STRATEGIES.contains(strategy);
   }
 
-  private class MergeWorker extends GitCloneWorker<MergeCommandResult> {
-
-    private final String target;
-    private final String toMerge;
-    private final Person author;
-    private final String messageTemplate;
-
-    private MergeWorker(Git clone, MergeCommandRequest request) {
-      super(clone);
-      this.target = request.getTargetBranch();
-      this.toMerge = request.getBranchToMerge();
-      this.author = request.getAuthor();
-      this.messageTemplate = request.getMessageTemplate();
-    }
-
-    @Override
-    MergeCommandResult run() throws IOException {
-      MergeResult result = doMergeInClone();
-      if (result.getMergeStatus().isSuccessful()) {
-        doCommit();
-        push();
-        return MergeCommandResult.success();
-      } else {
-        return analyseFailure(result);
-      }
-    }
-
-    private MergeResult doMergeInClone() throws IOException {
-      MergeResult result;
-      try {
-        ObjectId sourceRevision = resolveRevision(toMerge);
-        result = getClone().merge()
-          .setFastForward(FastForwardMode.NO_FF)
-          .setCommit(false) // we want to set the author manually
-          .include(toMerge, sourceRevision)
-          .call();
-      } catch (GitAPIException e) {
-        throw new InternalRepositoryException(context.getRepository(), "could not merge branch " + toMerge + " into " + target, e);
-      }
-      return result;
-    }
-
-    private void doCommit() {
-      logger.debug("merged branch {} into {}", toMerge, target);
-      doCommit(MessageFormat.format(determineMessageTemplate(), toMerge, target), author);
-    }
-
-    private String determineMessageTemplate() {
-      if (Strings.isNullOrEmpty(messageTemplate)) {
-        return MERGE_COMMIT_MESSAGE_TEMPLATE;
-      } else {
-        return messageTemplate;
-      }
-    }
-
-    private MergeCommandResult analyseFailure(MergeResult result) {
-      logger.info("could not merged branch {} into {} due to conflict in paths {}", toMerge, target, result.getConflicts().keySet());
-      return MergeCommandResult.failure(result.getConflicts().keySet());
-    }
+  @Override
+  public Set<MergeStrategy> getSupportedMergeStrategies() {
+    return STRATEGIES;
   }
 
   private class ConflictWorker extends GitCloneWorker<MergeConflictResult> {
@@ -133,7 +96,7 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
     private final WorkingCopyCloser closer;
 
     private ConflictWorker(Git git, MergeCommandRequest request, WorkingCopyCloser closer) {
-      super(git);
+      super(git, context, repository);
       this.git = git;
       this.request = request;
       this.closer = closer;
@@ -145,7 +108,7 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
       MergeResult mergeResult;
       try {
         mergeResult = getClone().merge()
-          .setFastForward(FastForwardMode.NO_FF)
+          .setFastForward(org.eclipse.jgit.api.MergeCommand.FastForwardMode.NO_FF)
           .setCommit(false)
           .include(request.getBranchToMerge(), sourceRevision)
           .call();

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

@@ -0,0 +1,31 @@
+package sonia.scm.repository.spi;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.MergeCommand;
+import org.eclipse.jgit.api.MergeResult;
+import sonia.scm.repository.Repository;
+import sonia.scm.repository.api.MergeCommandResult;
+
+import java.io.IOException;
+
+class GitMergeCommit extends GitMergeStrategy {
+
+  GitMergeCommit(Git clone, MergeCommandRequest request, GitContext context, Repository repository) {
+    super(clone, request, context, repository);
+  }
+
+  @Override
+  MergeCommandResult run() throws IOException {
+    MergeCommand mergeCommand = getClone().merge();
+    mergeCommand.setFastForward(MergeCommand.FastForwardMode.NO_FF);
+    MergeResult result = doMergeInClone(mergeCommand);
+
+    if (result.getMergeStatus().isSuccessful()) {
+      doCommit();
+      push();
+      return MergeCommandResult.success();
+    } else {
+      return analyseFailure(result);
+    }
+  }
+}

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

@@ -0,0 +1,72 @@
+package sonia.scm.repository.spi;
+
+import com.google.common.base.Strings;
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.MergeCommand;
+import org.eclipse.jgit.api.MergeResult;
+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.Person;
+import sonia.scm.repository.api.MergeCommandResult;
+
+import java.io.IOException;
+import java.text.MessageFormat;
+
+abstract class GitMergeStrategy extends AbstractGitCommand.GitCloneWorker<MergeCommandResult> {
+
+  private static final Logger logger = LoggerFactory.getLogger(GitMergeStrategy.class);
+
+  private static final String MERGE_COMMIT_MESSAGE_TEMPLATE = String.join("\n",
+    "Merge of branch {0} into {1}",
+    "",
+    "Automatic merge by SCM-Manager.");
+
+  private final String target;
+  private final String toMerge;
+  private final Person author;
+  private final String messageTemplate;
+
+  GitMergeStrategy(Git clone, MergeCommandRequest request, GitContext context, sonia.scm.repository.Repository repository) {
+    super(clone, context, repository);
+    this.target = request.getTargetBranch();
+    this.toMerge = request.getBranchToMerge();
+    this.author = request.getAuthor();
+    this.messageTemplate = request.getMessageTemplate();
+  }
+
+  MergeResult doMergeInClone(MergeCommand mergeCommand) throws IOException {
+    MergeResult result;
+    try {
+      ObjectId sourceRevision = resolveRevision(toMerge);
+      mergeCommand
+        .setCommit(false) // we want to set the author manually
+        .include(toMerge, sourceRevision);
+
+      result = mergeCommand.call();
+    } catch (GitAPIException e) {
+      throw new InternalRepositoryException(getContext().getRepository(), "could not merge branch " + toMerge + " into " + target, e);
+    }
+    return result;
+  }
+
+  void doCommit() {
+    logger.debug("merged branch {} into {}", toMerge, target);
+    doCommit(MessageFormat.format(determineMessageTemplate(), toMerge, target), author);
+  }
+
+  private String determineMessageTemplate() {
+    if (Strings.isNullOrEmpty(messageTemplate)) {
+      return MERGE_COMMIT_MESSAGE_TEMPLATE;
+    } else {
+      return messageTemplate;
+    }
+  }
+
+  MergeCommandResult analyseFailure(MergeResult result) {
+    logger.info("could not merge branch {} into {} due to conflict in paths {}", toMerge, target, result.getConflicts().keySet());
+    return MergeCommandResult.failure(result.getConflicts().keySet());
+  }
+}

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

@@ -0,0 +1,31 @@
+package sonia.scm.repository.spi;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.MergeResult;
+import sonia.scm.repository.Repository;
+import sonia.scm.repository.api.MergeCommandResult;
+import org.eclipse.jgit.api.MergeCommand;
+
+import java.io.IOException;
+
+class GitMergeWithSquash extends GitMergeStrategy {
+
+  GitMergeWithSquash(Git clone, MergeCommandRequest request, GitContext context, Repository repository) {
+    super(clone, request, context, repository);
+  }
+
+  @Override
+  MergeCommandResult run() throws IOException {
+   MergeCommand mergeCommand = getClone().merge();
+    mergeCommand.setSquash(true);
+    MergeResult result = doMergeInClone(mergeCommand);
+
+    if (result.getMergeStatus().isSuccessful()) {
+      doCommit();
+      push();
+      return MergeCommandResult.success();
+    } else {
+      return analyseFailure(result);
+    }
+  }
+}

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

@@ -46,7 +46,7 @@ public class GitModifyCommand extends AbstractGitCommand implements ModifyComman
     private final ModifyCommandRequest request;
 
     ModifyWorker(Git clone, ModifyCommandRequest request) {
-      super(clone);
+      super(clone, context, repository);
       this.workDir = clone.getRepository().getWorkTree();
       this.request = request;
     }

scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMergeCommandTest.java

@@ -15,10 +15,12 @@ import org.junit.Test;
 import sonia.scm.NotFoundException;
 import sonia.scm.repository.Person;
 import sonia.scm.repository.api.MergeCommandResult;
+import sonia.scm.repository.api.MergeStrategy;
 import sonia.scm.repository.util.WorkdirProvider;
 import sonia.scm.user.User;
 
 import java.io.IOException;
+import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -62,6 +64,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     MergeCommandRequest request = new MergeCommandRequest();
     request.setTargetBranch("master");
     request.setBranchToMerge("mergeable");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
     request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
 
     MergeCommandResult mergeCommandResult = command.merge(request);
@@ -88,6 +91,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     MergeCommandRequest request = new MergeCommandRequest();
     request.setTargetBranch("master");
     request.setBranchToMerge("empty_merge");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
     request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
 
     MergeCommandResult mergeCommandResult = command.merge(request);
@@ -109,6 +113,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     request.setTargetBranch("master");
     request.setBranchToMerge("mergeable");
     request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
 
     MergeCommandResult mergeCommandResult = command.merge(request);
 
@@ -132,6 +137,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     MergeCommandRequest request = new MergeCommandRequest();
     request.setTargetBranch("master");
     request.setBranchToMerge("mergeable");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
     request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
     request.setMessageTemplate("simple");
 
@@ -152,6 +158,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     MergeCommandRequest request = new MergeCommandRequest();
     request.setBranchToMerge("test-branch");
     request.setTargetBranch("master");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
 
     MergeCommandResult mergeCommandResult = command.merge(request);
 
@@ -173,6 +180,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     MergeCommandRequest request = new MergeCommandRequest();
     request.setTargetBranch("master");
     request.setBranchToMerge("mergeable");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
 
     MergeCommandResult mergeCommandResult = command.merge(request);
 
@@ -192,6 +200,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
     request.setTargetBranch("mergeable");
     request.setBranchToMerge("master");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
 
     MergeCommandResult mergeCommandResult = command.merge(request);
 
@@ -211,12 +220,112 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     assertThat(new String(contentOfFileB)).isEqualTo("b\ncontent from branch\n");
   }
 
+  @Test
+  public void shouldSquashCommitsIfSquashIsEnabled() throws IOException, GitAPIException {
+    GitMergeCommand command = createCommand();
+    MergeCommandRequest request = new MergeCommandRequest();
+    request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
+    request.setBranchToMerge("squash");
+    request.setTargetBranch("master");
+    request.setMessageTemplate("this is a squash");
+    request.setMergeStrategy(MergeStrategy.SQUASH);
+
+    MergeCommandResult mergeCommandResult = command.merge(request);
+
+    Repository repository = createContext().open();
+    assertThat(mergeCommandResult.isSuccess()).isTrue();
+
+    Iterable<RevCommit> commits = new Git(repository).log().add(repository.resolve("master")).setMaxCount(1).call();
+    RevCommit mergeCommit = commits.iterator().next();
+    PersonIdent mergeAuthor = mergeCommit.getAuthorIdent();
+    String message = mergeCommit.getFullMessage();
+    assertThat(mergeAuthor.getName()).isEqualTo("Dirk Gently");
+    assertThat(message).isEqualTo("this is a squash");
+  }
+
+  @Test
+  public void shouldSquashThreeCommitsIntoOne() throws IOException, GitAPIException {
+    GitMergeCommand command = createCommand();
+    MergeCommandRequest request = new MergeCommandRequest();
+    request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
+    request.setBranchToMerge("squash");
+    request.setTargetBranch("master");
+    request.setMessageTemplate("squash three commits");
+    request.setMergeStrategy(MergeStrategy.SQUASH);
+    Repository gitRepository = createContext().open();
+    MergeCommandResult mergeCommandResult = command.merge(request);
+
+    assertThat(mergeCommandResult.isSuccess()).isTrue();
+
+    Iterable<RevCommit> commits = new Git(gitRepository).log().add(gitRepository.resolve("master")).setMaxCount(1).call();
+    RevCommit mergeCommit = commits.iterator().next();
+    PersonIdent mergeAuthor = mergeCommit.getAuthorIdent();
+    String message = mergeCommit.getFullMessage();
+    assertThat(mergeAuthor.getName()).isEqualTo("Dirk Gently");
+    assertThat(message).isEqualTo("squash three commits");
+
+    GitModificationsCommand modificationsCommand = new GitModificationsCommand(createContext(), repository);
+    List<String> changes = modificationsCommand.getModifications("master").getAdded();
+    assertThat(changes.size()).isEqualTo(3);
+  }
+
+
+  @Test
+  public void shouldMergeWithFastForward() throws IOException, GitAPIException {
+    Repository repository = createContext().open();
+
+    ObjectId featureBranchHead = new Git(repository).log().add(repository.resolve("squash")).setMaxCount(1).call().iterator().next().getId();
+
+    GitMergeCommand command = createCommand();
+    MergeCommandRequest request = new MergeCommandRequest();
+    request.setBranchToMerge("squash");
+    request.setTargetBranch("master");
+    request.setMergeStrategy(MergeStrategy.FAST_FORWARD_IF_POSSIBLE);
+    request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
+
+    MergeCommandResult mergeCommandResult = command.merge(request);
+
+    assertThat(mergeCommandResult.isSuccess()).isTrue();
+
+    Iterable<RevCommit> commits = new Git(repository).log().add(repository.resolve("master")).setMaxCount(1).call();
+    RevCommit mergeCommit = commits.iterator().next();
+    assertThat(mergeCommit.getParentCount()).isEqualTo(1);
+    PersonIdent mergeAuthor = mergeCommit.getAuthorIdent();
+    assertThat(mergeAuthor.getName()).isEqualTo("Philip J Fry");
+    assertThat(mergeCommit.getId()).isEqualTo(featureBranchHead);
+  }
+
+  @Test
+  public void shouldDoMergeCommitIfFastForwardIsNotPossible() throws IOException, GitAPIException {
+    GitMergeCommand command = createCommand();
+    MergeCommandRequest request = new MergeCommandRequest();
+    request.setTargetBranch("master");
+    request.setBranchToMerge("mergeable");
+    request.setMergeStrategy(MergeStrategy.FAST_FORWARD_IF_POSSIBLE);
+    request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
+
+    MergeCommandResult mergeCommandResult = command.merge(request);
+
+    assertThat(mergeCommandResult.isSuccess()).isTrue();
+
+    Repository repository = createContext().open();
+    Iterable<RevCommit> commits = new Git(repository).log().add(repository.resolve("master")).setMaxCount(1).call();
+    RevCommit mergeCommit = commits.iterator().next();
+    PersonIdent mergeAuthor = mergeCommit.getAuthorIdent();
+    assertThat(mergeCommit.getParentCount()).isEqualTo(2);
+    String message = mergeCommit.getFullMessage();
+    assertThat(mergeAuthor.getName()).isEqualTo("Dirk Gently");
+    assertThat(mergeAuthor.getEmailAddress()).isEqualTo("dirk@holistic.det");
+    assertThat(message).contains("master", "mergeable");
+  }
+
   @Test(expected = NotFoundException.class)
   public void shouldHandleNotExistingSourceBranchInMerge() {
     GitMergeCommand command = createCommand();
     MergeCommandRequest request = new MergeCommandRequest();
     request.setTargetBranch("mergeable");
     request.setBranchToMerge("not_existing");
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
 
     command.merge(request);
   }
@@ -225,6 +334,7 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
   public void shouldHandleNotExistingTargetBranchInMerge() {
     GitMergeCommand command = createCommand();
     MergeCommandRequest request = new MergeCommandRequest();
+    request.setMergeStrategy(MergeStrategy.MERGE_COMMIT);
     request.setTargetBranch("not_existing");
     request.setBranchToMerge("master");