Throw exception when no changes were made

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

@@ -43,6 +43,7 @@ import org.eclipse.jgit.api.errors.RefNotFoundException;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import sonia.scm.repository.GitUtil;
@@ -55,7 +56,10 @@ import sonia.scm.user.User;
 import java.io.IOException;
 import java.util.Optional;
 import java.util.function.Function;
+import java.util.function.Supplier;
 
+import static java.util.Optional.empty;
+import static java.util.Optional.of;
 import static sonia.scm.ContextEntry.ContextBuilder.entity;
 import static sonia.scm.NotFoundException.notFound;
 
@@ -200,14 +204,26 @@ class AbstractGitCommand
       }
     }
 
-    void doCommit(String message, Person author) {
+    void failIfNotChanged(Supplier<RuntimeException> doThrow) {
+      try {
+        if (clone.status().call().isClean()) {
+          throw doThrow.get();
+        }
+      } catch (GitAPIException e) {
+        throw new InternalRepositoryException(context.getRepository(), "could not read status of repository", e);
+      }
+    }
+
+    Optional<RevCommit> doCommit(String message, Person author) {
       Person authorToUse = determineAuthor(author);
       try {
         if (!clone.status().call().isClean()) {
-          clone.commit()
+          return of(clone.commit()
             .setAuthor(authorToUse.getName(), authorToUse.getMail())
             .setMessage(message)
-            .call();
+            .call());
+        } else {
+          return empty();
         }
       } catch (GitAPIException e) {
         throw new InternalRepositoryException(context.getRepository(), "could not commit changes", e);

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

@@ -2,6 +2,8 @@ package sonia.scm.repository.spi;
 
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.errors.GitAPIException;
+import sonia.scm.BadRequestException;
+import sonia.scm.ContextEntry;
 import sonia.scm.repository.GitWorkdirFactory;
 import sonia.scm.repository.InternalRepositoryException;
 import sonia.scm.repository.Repository;
@@ -44,9 +46,10 @@ public class GitModifyCommand extends AbstractGitCommand implements ModifyComman
     @Override
     String run() throws IOException {
       checkOutBranch(request.getBranch());
-      for (ModifyCommandRequest.PartialRequest r: request.getRequests()) {
+      for (ModifyCommandRequest.PartialRequest r : request.getRequests()) {
         r.execute(this);
       }
+      failIfNotChanged(NoChangesMadeException::new);
       doCommit(request.getCommitMessage(), request.getAuthor());
       push();
       return getClone().getRepository().getRefDatabase().findRef("HEAD").getObjectId().name();
@@ -86,6 +89,17 @@ public class GitModifyCommand extends AbstractGitCommand implements ModifyComman
     public void move(String sourcePath, String targetPath) {
 
     }
+
+    private class NoChangesMadeException extends BadRequestException {
+      public NoChangesMadeException() {
+        super(ContextEntry.ContextBuilder.entity(context.getRepository()).build(), "no changes detected to branch " + ModifyWorker.this.request.getBranch());
+      }
+
+      @Override
+      public String getCode() {
+        return "40RaYIeeR1";
+      }
+    }
   }
 
   private String throwInternalRepositoryException(String message, Exception e) {

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

@@ -14,6 +14,7 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 import sonia.scm.AlreadyExistsException;
+import sonia.scm.BadRequestException;
 import sonia.scm.repository.Person;
 import sonia.scm.repository.util.WorkdirProvider;
 
@@ -108,6 +109,21 @@ public class GitModifyCommandTest extends AbstractGitCommandTestBase {
     assertInTree(assertions);
   }
 
+  @Test(expected = BadRequestException.class)
+  public void shouldFailIfNoChangesMade() throws IOException, GitAPIException {
+    File newFile = Files.write(temporaryFolder.newFile().toPath(), "b\n".getBytes()).toFile();
+
+    GitModifyCommand command = createCommand();
+
+    ModifyCommandRequest request = new ModifyCommandRequest();
+    request.setBranch("master");
+    request.setCommitMessage("test commit");
+    request.addRequest(new ModifyCommandRequest.CreateFileRequest("b.txt", newFile, true));
+    request.setAuthor(new Person("Dirk Gently", "dirk@holistic.det"));
+
+    command.execute(request);
+  }
+
   private void assertInTree(TreeAssertions assertions) throws IOException, GitAPIException {
     try (Git git = new Git(createContext().open())) {
       RevCommit lastCommit = getLastCommit(git);