The Compose file read uses a sparse clone without a checkout, so submodules
were never cloned. Now only the submodule that contains the Compose file is
cloned, with the credentials of the clone.
Closes#11018
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Apply HTTP/1.1 transport config to HTTPS git clone and submodule commands,
including GitHub App credential rewrites, to avoid flaky large repo imports.
Use per-command git config for GitHub App HTTPS credentials so private submodules authenticate without persisting global git config. Preserve configured git options for checkout, fetch, submodule, and LFS commands, and cover GitLab PR submodule checkout with tests.