Don't generate warnings on missing formatters for symlinks to directories

[Mic92]

Treefmt seems to use lstat instead of stat to figure out a filetype?
It leads to some odd behavior when symlinks to directories are used.
Treefmt should not generate warnings for directories.

~/.homesick/repos/dotfiles test-foo* ⇡
nix-shell-env % nix fmt
2024/12/10 06:14:01 INFO using config file: /nix/store/9skqqjkkajkf44rg1ani1l0bcyr75cq1-treefmt.toml
WARN no formatter for path: home/.config/nixpkgs
WARN no formatter for path: home/.fast-syntax-highlighting
WARN no formatter for path: home/.gef-extras
WARN no formatter for path: home/.gef-mic92
traversed 999 files
emitted 346 files for processing
formatted 1 files (0 changed) in 31ms

~/.homesick/repos/dotfiles test-foo* ⇡
nix-shell-env % ls -la home/.gef-*
lrwxrwxrwx joerg users 17 B 5 months ago  home/.gef-extras@ ⇒ ../gdb/gef-extras
lrwxrwxrwx joerg users 16 B 5 months ago  home/.gef-mic92@ ⇒ ../gdb/gef-mic92

nix-shell-env % stat home/.gef-extras
  File: home/.gef-extras -> ../gdb/gef-extras
  Size: 17              Blocks: 1          IO Block: 512    symbolic link
Device: 0,53    Inode: 6577745     Links: 1
Access: (0777/lrwxrwxrwx)  Uid: ( 1000/   joerg)   Gid: (  100/   users)
Access: 2024-12-09 09:00:15.636895706 +0100
Modify: 2024-07-01 16:23:33.678525570 +0200
Change: 2024-07-01 16:23:45.254346582 +0200
 Birth: 2024-07-01 16:23:33.678525570 +0200

stat ./gdb/gef-extras
  File: ./gdb/gef-extras
  Size: 19              Blocks: 17         IO Block: 1536   directory
Device: 0,53    Inode: 132444      Links: 9
Access: (0755/drwxr-xr-x)  Uid: ( 1000/   joerg)   Gid: (  100/   users)
Access: 2024-12-09 08:42:23.294971942 +0100
Modify: 2024-10-31 10:32:46.812263967 +0100
Change: 2024-10-31 10:32:46.812263967 +0100
 Birth: 2024-07-01 16:23:33.494528414 +0200

[zimbatm]

It should probably skip symlink directories entirely. There is potentially an attack/bug if the symlink points outside of the directory as well.

[Mic92]

The directory is still within the repository.