Start tasks in a repo with no commits

internal/agents/tasks.go

@@ -119,6 +119,17 @@ func (m *Manager) createTask(ctx context.Context, project api.Project, t api.Tas
 	t.Status = api.TaskStatusActive
 	t.CreatedAt = time.Now().UTC()
 
+	if base == project.DefaultBranch {
+		creator, err := m.store.GetUser(ctx, t.CreatedBy)
+		if err != nil {
+			return api.Task{}, err
+		}
+		err = git.EnsureBranchCommit(ctx, project.RepoPath, base, git.IdentityEnv(creator.GitName, creator.GitEmail))
+		if err != nil {
+			return api.Task{}, err
+		}
+	}
+
 	var err error
 	t.BaseRef, err = git.AddWorktree(ctx, project.RepoPath, t.WorktreePath, t.Branch, base)
 	if err != nil {

internal/git/git.go

@@ -75,6 +75,27 @@ func AddWorktree(ctx context.Context, repo, path, branch, base string) (string,
 	return sha, nil
 }
 
+func EnsureBranchCommit(ctx context.Context, repo, branch string, env []string) error {
+	_, _, code, err := runCode(ctx, repo, nil, "rev-parse", "--verify", "--quiet", "refs/heads/"+branch+"^{commit}")
+	if err != nil || code == 0 {
+		return err
+	}
+	refs, err := run(ctx, repo, "for-each-ref", "--count=1")
+	if err != nil || refs != "" {
+		return err
+	}
+	tree, err := run(ctx, repo, "mktree")
+	if err != nil {
+		return err
+	}
+	commit, err := runEnv(ctx, repo, env, "commit-tree", tree, "-m", "Initial commit")
+	if err != nil {
+		return err
+	}
+	_, err = run(ctx, repo, "update-ref", "refs/heads/"+branch, commit, "")
+	return err
+}
+
 func AddDetachedWorktree(ctx context.Context, repo, path, commit string) error {
 	_, err := run(ctx, repo, "worktree", "add", "--detach", path, commit)
 	return err