Set HEAD to correct default branch (#1929)

Sets the HEAD for new Git repositories to the default branch (this is 'main' for the default configuration).
This change led to errors in unit tests, that depended on the 'master' branch.

Co-authored-by: Eduard Heimbuch <eduard.heimbuch@cloudogu.com>

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

@@ -183,6 +183,7 @@ public class GitRepositoryHandler
   protected void create(Repository repository, File directory) throws IOException {
     try (org.eclipse.jgit.lib.Repository gitRepository = build(directory)) {
       gitRepository.create(true);
+      new GitHeadModifier(this).ensure(repository, config.getDefaultBranch());
       new GitConfigHelper().createScmmConfig(repository, gitRepository);
     }
   }

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

@@ -84,7 +84,7 @@ public final class GitUtil {
   private static final GitUserAgentProvider GIT_USER_AGENT_PROVIDER = new GitUserAgentProvider();
   public static final String REF_HEAD = "HEAD";
   public static final String REF_HEAD_PREFIX = "refs/heads/";
-  public static final String REF_MASTER = "master";
+  public static final String REF_MAIN = "main";
   private static final String DIRECTORY_DOTGIT = ".git";
   private static final String DIRECTORY_OBJETCS = "objects";
   private static final String DIRECTORY_REFS = "refs";
@@ -425,7 +425,7 @@ public final class GitUtil {
       return of(refHead.getTarget());
     }
 
-    Ref master = refs.get(REF_HEAD_PREFIX + REF_MASTER);
+    Ref master = refs.get(REF_HEAD_PREFIX + REF_MAIN);
     if (master != null) {
       return of(master);
     }

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

@@ -24,8 +24,6 @@
 
 package sonia.scm.repository;
 
-//~--- non-JDK imports --------------------------------------------------------
-
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -36,13 +34,12 @@ import sonia.scm.store.ConfigurationStoreFactory;
 
 import java.io.File;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.when;
 
-//~--- JDK imports ------------------------------------------------------------
-
 /**
  * @author Sebastian Sdorra
  */
@@ -112,4 +109,21 @@ public class GitRepositoryHandlerTest extends SimpleRepositoryHandlerTestBase {
     File path = repositoryHandler.getDirectory(repository.getId());
     assertEquals(repoPath.toString() + File.separator + RepositoryDirectoryHandler.REPOSITORIES_NATIVE_DIRECTORY, path.getAbsolutePath());
   }
+
+  @Test
+  public void shouldSetHeadToDefaultRepository() {
+    GitRepositoryHandler repositoryHandler = new GitRepositoryHandler(factory,
+      scheduler, locationResolver, gitWorkingCopyFactory, null);
+
+    GitConfig config = new GitConfig();
+    config.setDefaultBranch("other");
+
+    repositoryHandler.setConfig(config);
+
+    File nativeRepoDirectory = initRepository();
+
+    repositoryHandler.create(repository);
+
+    assertThat(new File(nativeRepoDirectory, "HEAD")).hasContent("ref: refs/heads/other");
+  }
 }

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

@@ -295,7 +295,7 @@ public class GitLogCommandTest extends AbstractGitCommandTestBase
 
     ChangesetPagingResult changesets = createCommand().getChangesets(new LogCommandRequest());
 
-    assertEquals("master", changesets.getBranchName());
+    assertEquals("main", changesets.getBranchName());
   }
 
   @Test