Regression in 0.149.0: empty .git directory no longer defines the project root

What changed

After upgrading Codex CLI from 0.148.0 to 0.149.0, an empty .git directory no longer stops the upward project-root search. In a child directory inside a parent Git repository, the terminal title now resolves to the parent repository name.

In 0.148.0, the check was:

if dot_git.exists()

In 0.149.0, it became:

if dot_git.exists() && (!dot_git.is_dir() || dot_git.join("HEAD").exists())

Adding an empty .git/HEAD file restores the old behavior.

Relevant comparison: https://github.com/openai/codex/compare/rust-v0.148.0...rust-v0.149.0

Suggestion

Please consider removing the additional HEAD existence check and restoring the 0.148.0 behavior. A .git directory is normally created either by Git or intentionally by the user. In the intentional case, the user knows they are using it as a project boundary.

Environment

• Codex CLI 0.149.0
• Windows 11 / PowerShell

Compare the project-root search logic between rust-v0.148.0 and rust-v0.149.0, starting from the .git existence check described in the issue. Restore the behavior where an empty .git directory defines the project boundary, then verify that a child directory inside a parent repository resolves to the intended project root.