Add command api for dry run merge

scm-core/src/main/java/sonia/scm/repository/api/Command.java

@@ -71,5 +71,10 @@ public enum Command
   /**
    * @since 2.0
    */
-  MERGE
+  MERGE,
+
+  /**
+   * @since 2.0
+   */
+  MERGE_DRY_RUN
 }

scm-core/src/main/java/sonia/scm/repository/api/MergeDryRunCommandBuilder.java

@@ -0,0 +1,35 @@
+package sonia.scm.repository.api;
+
+import com.google.common.base.Preconditions;
+import sonia.scm.repository.spi.MergeCommand;
+import sonia.scm.repository.spi.MergeCommandRequest;
+
+public class MergeDryRunCommandBuilder {
+
+  private final MergeCommand mergeCommand;
+  private final MergeCommandRequest request = new MergeCommandRequest();
+
+  public MergeDryRunCommandBuilder(MergeCommand mergeCommand) {
+    this.mergeCommand = mergeCommand;
+  }
+
+  public MergeDryRunCommandBuilder setBranchToMerge(String branchToMerge) {
+    request.setBranchToMerge(branchToMerge);
+    return this;
+  }
+
+  public MergeDryRunCommandBuilder setTargetBranch(String targetBranch) {
+    request.setTargetBranch(targetBranch);
+    return this;
+  }
+
+  public MergeDryRunCommandBuilder reset() {
+    request.reset();
+    return this;
+  }
+
+  public boolean execute() {
+    Preconditions.checkArgument(request.isValid(), "revision to merge and target revision is required");
+    return mergeCommand.merge(request);
+  }
+}

scm-core/src/main/java/sonia/scm/repository/spi/MergeDryRunCommand.java

@@ -0,0 +1,5 @@
+package sonia.scm.repository.spi;
+
+public interface MergeDryRunCommand {
+  boolean isMergeable(MergeDryRunCommandRequest request);
+}

scm-core/src/main/java/sonia/scm/repository/spi/MergeDryRunCommandRequest.java

@@ -0,0 +1,70 @@
+package sonia.scm.repository.spi;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.base.Objects;
+import com.google.common.base.Strings;
+import sonia.scm.Validateable;
+
+import java.io.Serializable;
+
+public class MergeDryRunCommandRequest implements Validateable, Resetable, Serializable, Cloneable {
+
+  private static final long serialVersionUID = -2650236557922431528L;
+
+  private String branchToMerge;
+  private String targetBranch;
+
+  public String getBranchToMerge() {
+    return branchToMerge;
+  }
+
+  public void setBranchToMerge(String branchToMerge) {
+    this.branchToMerge = branchToMerge;
+  }
+
+  public String getTargetBranch() {
+    return targetBranch;
+  }
+
+  public void setTargetBranch(String targetBranch) {
+    this.targetBranch = targetBranch;
+  }
+
+  public boolean isValid() {
+    return !Strings.isNullOrEmpty(getBranchToMerge()) && !Strings.isNullOrEmpty(getTargetBranch());
+  }
+
+  public void reset() {
+    this.setBranchToMerge(null);
+    this.setTargetBranch(null);
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (obj == null) {
+      return false;
+    }
+
+    if (getClass() != obj.getClass()) {
+      return false;
+    }
+
+    final MergeDryRunCommandRequest other = (MergeDryRunCommandRequest) obj;
+
+    return Objects.equal(branchToMerge, other.branchToMerge)
+      && Objects.equal(targetBranch, other.targetBranch);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hashCode(branchToMerge, targetBranch);
+  }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+      .add("branchToMerge", branchToMerge)
+      .add("targetBranch", targetBranch)
+      .toString();
+  }
+}

scm-core/src/main/java/sonia/scm/repository/spi/RepositoryServiceProvider.java

@@ -259,4 +259,12 @@ public abstract class RepositoryServiceProvider implements Closeable
   {
     throw new CommandNotSupportedException(Command.MERGE);
   }
+
+  /**
+   * @since 2.0
+   */
+  public MergeDryRunCommand getMergeDryRunCommand()
+  {
+    throw new CommandNotSupportedException(Command.MERGE_DRY_RUN);
+  }
 }