Implement branch provider to prevent errors

The review plugin does not explicitly check, if the
branch provider is supported in events. It only checks,
whether the repository supports branches per se.
Therefor, if a tag is created from the ui, an internal server
error is thrown. We prevent this by implementing a
simple branch provider here, too.

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

@@ -41,6 +41,7 @@ import sonia.scm.repository.PreReceiveRepositoryHookEvent;
 import sonia.scm.repository.RepositoryHookEvent;
 import sonia.scm.repository.RepositoryHookType;
 import sonia.scm.repository.Tag;
+import sonia.scm.repository.api.HookBranchProvider;
 import sonia.scm.repository.api.HookChangesetProvider;
 import sonia.scm.repository.api.HookContext;
 import sonia.scm.repository.api.HookContextFactory;
@@ -220,6 +221,21 @@ public class GitTagCommand extends AbstractGitCommand implements TagCommand {
       };
     }
 
+    @Override
+    public HookBranchProvider getBranchProvider() {
+      return new HookBranchProvider() {
+        @Override
+        public List<String> getCreatedOrModified() {
+          return List.of();
+        }
+
+        @Override
+        public List<String> getDeletedOrClosed() {
+          return List.of();
+        }
+      };
+    }
+
     @Override
     public HookChangesetProvider getChangesetProvider() {
       Collection<ReceiveCommand> receiveCommands = new ArrayList<>();