Re: [PATCH v4] setup: allow cwd/.git to be a symlink to a directory

> Strictly enforcing 'lstat()' and 'S_ISREG()' on '.git' prevents valid
> workflows where '.git' is a symbolic link pointing to a real git
> directory (e.g. created via 'ln -s').
>
> Refactor 'setup_git_directory_gently_1()' to use 'stat()' instead of
> 'lstat()'. This allows the filesystem to automatically resolve symbolic
> links.
>
> To ensure safety and correctness, the logic flow is updated to:
>
> 1. Ignore 'ENOENT' (file missing).
> 2. Check 'IS_A_DIR' cases via 'is_git_directory()'.
> 3. Explicitly reject 'NOT_A_FILE' cases (FIFOs or sockets).
>
> Add a new test script t/t0009-setup-security.sh which verifies:
>
> - Valid .git symlinks to real directories are accepted.
> - .git as a named pipe (FIFO) is rejected.
> - .git as a symlink to a named pipe is rejected.
> - .git with garbage content is rejected.
> - Empty .git directories are ignored.
>
> Signed-off-by: Tian Yuchen <a3205153416@gmail.com>
> ---
>  setup.c                   | 39 ++++++++++++++-------
>  setup.h                   |  2 ++
>  t/t0009-setup-security.sh | 72 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 101 insertions(+), 12 deletions(-)
>  create mode 100755 t/t0009-setup-security.sh
>