Merged in bugfix/empty_merge_git (pull request #334)

do merge commit also without diffs between branches

Approved-by: Rene Pfeuffer <rene.pfeuffer@cloudogu.com>

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

@@ -38,6 +38,7 @@ import com.google.common.base.Strings;
 import org.apache.shiro.SecurityUtils;
 import org.apache.shiro.subject.Subject;
 import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.Status;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.api.errors.RefNotFoundException;
 import org.eclipse.jgit.lib.ObjectId;
@@ -217,7 +218,8 @@ class AbstractGitCommand
     Optional<RevCommit> doCommit(String message, Person author) {
       Person authorToUse = determineAuthor(author);
       try {
-        if (!clone.status().call().isClean()) {
+        Status status = clone.status().call();
+        if (!status.isClean() || isInMerge()) {
           return of(clone.commit()
             .setAuthor(authorToUse.getName(), authorToUse.getMail())
             .setMessage(message)
@@ -225,11 +227,15 @@ class AbstractGitCommand
         } else {
           return empty();
         }
-      } catch (GitAPIException e) {
+      } catch (GitAPIException | IOException e) {
         throw new InternalRepositoryException(context.getRepository(), "could not commit changes", e);
       }
     }
 
+    private boolean isInMerge() throws IOException {
+      return clone.getRepository().readMergeHeads() != null && !clone.getRepository().readMergeHeads().isEmpty();
+    }
+
     void push() {
       try {
         clone.push().call();

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

@@ -82,6 +82,26 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     assertThat(new String(contentOfFileB)).isEqualTo("b\ncontent from branch\n");
   }
 
+  @Test
+  public void shouldAllowEmptyMergeCommit() throws IOException, GitAPIException {
+    GitMergeCommand command = createCommand();
+    MergeCommandRequest request = new MergeCommandRequest();
+    request.setTargetBranch("master");
+    request.setBranchToMerge("empty_merge");
+    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();
+    assertThat(mergeCommit.getParentCount()).isEqualTo(2);
+    assertThat(mergeCommit.getParent(0).name()).isEqualTo("fcd0ef1831e4002ac43ea539f4094334c79ea9ec");
+    assertThat(mergeCommit.getParent(1).name()).isEqualTo("d81ad6c63d7e2162308d69637b339dedd1d9201c");
+  }
+
   @Test
   public void shouldNotMergeTwice() throws IOException, GitAPIException {
     GitMergeCommand command = createCommand();