リポジトリのコードの行数の合計値を取得するには

git ls-files

コマンドでリポジトリ内のファイルを一覧で表示します

xargs wc

のオプションを追加することで左から行数、単語数、バイト数を表示し、
-lオプションで行数のみ表示させることができます

git ls-files | xargs wc -l
      50 .github/workflows/deploy-storybook.yml
     130 .gitignore
      19 Makefile
      16 README.md
       4 application/.env
       3 application/.eslintrc.json
      31 application/.storybook/main.ts
       7 application/__test__/handlers.ts
      22 application/__test__/mocks/authinfo/index.ts
       0 application/__test__/mocks/user/index.ts
       4 application/__test__/node.ts
      22 application/__test__/unit/login.test.tsx
      11 application/components/elements/Task.jsx
      35 application/components/elements/Task.stories.jsx
      22 application/components/elements/input.tsx
      72 application/features/LoginForm.tsx
      74 application/features/fetch.ts
      31 application/jest.config.js
      29 application/jest.polyfills.js
      10 application/jest.setup.ts
       5 application/next-env.d.ts
      13 application/next.config.js
   22387 application/package-lock.json
      64 application/package.json
       9 application/pages/404/index.tsx
       6 application/pages/_app.tsx
      13 application/pages/_document.tsx
      11 application/pages/index.tsx
       9 application/pages/top/index.tsx
       6 application/postcss.config.js
      30 application/public/favicon.ico
       0 application/public/next.svg
       0 application/public/vercel.svg
       3 application/styles/globals.css
      82 application/tailwind.config.ts
      23 application/tsconfig.json
       4 application/types/index.ts
   23257 total

また、以下のようにgrepを使って特定の拡張子を持つコードの行数の合計値を取得できます

git ls-files | grep '\.ts' | xargs wc -l
      31 application/.storybook/main.ts
       7 application/__test__/handlers.ts
      22 application/__test__/mocks/authinfo/index.ts
       0 application/__test__/mocks/user/index.ts
       4 application/__test__/node.ts
      22 application/__test__/unit/login.test.tsx
      22 application/components/elements/input.tsx
      72 application/features/LoginForm.tsx
      74 application/features/fetch.ts
      10 application/jest.setup.ts
       5 application/next-env.d.ts
       9 application/pages/404/index.tsx
       6 application/pages/_app.tsx
      13 application/pages/_document.tsx
      11 application/pages/index.tsx
       9 application/pages/top/index.tsx
      82 application/tailwind.config.ts
       4 application/types/index.ts
     403 total

以上です

参考