Implement first steps for merge

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

@@ -0,0 +1,25 @@
+package sonia.scm.repository;
+
+import java.util.function.Consumer;
+
+public class CloseableWrapper<C> implements AutoCloseable {
+
+  private final C wrapped;
+  private final Consumer<C> cleanup;
+
+  public CloseableWrapper(C wrapped, Consumer<C> cleanup) {
+    this.wrapped = wrapped;
+    this.cleanup = cleanup;
+  }
+
+  public C get() { return wrapped; }
+
+  @Override
+  public void close() {
+    try {
+      cleanup.accept(wrapped);
+    } catch (Throwable t) {
+      throw new RuntimeException(t);
+    }
+  }
+}

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

@@ -90,6 +90,8 @@ public class GitRepositoryHandler
   private static final Object LOCK = new Object();
   
   private final Scheduler scheduler;
+
+  private final GitWorkdirPool workdirPool;
   
   private Task task;
   
@@ -104,10 +106,11 @@ public class GitRepositoryHandler
    * @param scheduler
    */
   @Inject
-  public GitRepositoryHandler(ConfigurationStoreFactory storeFactory, FileSystem fileSystem, Scheduler scheduler)
+  public GitRepositoryHandler(ConfigurationStoreFactory storeFactory, FileSystem fileSystem, Scheduler scheduler, GitWorkdirPool workdirPool)
   {
     super(storeFactory, fileSystem);
     this.scheduler = scheduler;
+    this.workdirPool = workdirPool;
   }
 
   //~--- get methods ----------------------------------------------------------
@@ -235,4 +238,8 @@ public class GitRepositoryHandler
   {
     return new File(directory, DIRECTORY_REFS).exists();
   }
+
+  public GitWorkdirPool getWorkdirPool() {
+    return workdirPool;
+  }
 }

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

@@ -0,0 +1,46 @@
+package sonia.scm.repository;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.lib.Repository;
+
+import java.io.File;
+import java.util.Random;
+
+
+/**
+ * Config:
+ *
+ * 1. Overall and absolute maximum of temp work directories
+ * 2. Maximum number of temp work directories pooled overall
+ * 3. Maximum number of temp work directories pooled for one master repository
+ */
+public class GitWorkdirPool {
+
+  private final Random random = new Random();
+  private final File poolDirectory;
+
+  public GitWorkdirPool() {
+    this(new File(System.getProperty("java.io.tmpdir")));
+  }
+
+  public GitWorkdirPool(File poolDirectory) {
+    this.poolDirectory = poolDirectory;
+  }
+
+  public CloseableWrapper<Repository> getWorkingCopy(File bareRepository) {
+    try {
+      Git clone = cloneRepository(bareRepository, new File(poolDirectory, Long.toString(random.nextLong())));
+      return new CloseableWrapper<>(clone.getRepository(), r -> clone.close());
+    } catch (GitAPIException e) {
+      throw new InternalRepositoryException("could not clone working copy of repository", e);
+    }
+  }
+
+  protected Git cloneRepository(File bareRepository, File target) throws GitAPIException {
+    return Git.cloneRepository()
+      .setURI(bareRepository.getAbsolutePath())
+      .setDirectory(target)
+      .call();
+  }
+}

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

@@ -0,0 +1,35 @@
+package sonia.scm.repository.spi;
+
+import org.eclipse.jgit.merge.MergeStrategy;
+import org.eclipse.jgit.merge.ResolveMerger;
+import sonia.scm.repository.CloseableWrapper;
+import sonia.scm.repository.GitWorkdirPool;
+import sonia.scm.repository.InternalRepositoryException;
+import sonia.scm.repository.Repository;
+
+import java.io.IOException;
+
+public class GitMergeCommand extends AbstractGitCommand implements MergeCommand {
+
+  private final GitWorkdirPool workdirPool;
+
+  GitMergeCommand(GitContext context, Repository repository, GitWorkdirPool workdirPool) {
+    super(context, repository);
+    this.workdirPool = workdirPool;
+  }
+
+  @Override
+  public boolean merge(MergeCommandRequest request) {
+    try (CloseableWrapper<org.eclipse.jgit.lib.Repository> workingCopy = workdirPool.getWorkingCopy(context.open().getDirectory())) {
+      org.eclipse.jgit.lib.Repository repository = workingCopy.get();
+      ResolveMerger merger = (ResolveMerger) MergeStrategy.RECURSIVE.newMerger(repository);
+      boolean mergeResult = merger.merge(repository.resolve(request.getBranchToMerge()), repository.resolve(request.getTargetBranch()));
+      if (mergeResult) {
+        // TODO push and verify push was successful
+      }
+      return mergeResult;
+    } catch (IOException e) {
+      throw new InternalRepositoryException(e);
+    }
+  }
+}

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

@@ -245,6 +245,12 @@ public class GitRepositoryServiceProvider extends RepositoryServiceProvider
   public MergeDryRunCommand getMergeDryRunCommand() {
     return new GitMergeDryRunCommand(context, repository);
   }
+
+  @Override
+  public MergeCommand getMergeCommand() {
+    return new GitMergeCommand(context, repository, handler.getWorkdirPool());
+  }
+
 //~--- fields ---------------------------------------------------------------
 
   /** Field description */