The search for the config file ignores symlinks

When placing a .rustfmt.toml file in my home directory (I realize you're meant to stay with the defaults globally, but wanted to switch to rfc style), I noticed it had no effect. Now, the folder my project was in is symlinked as ~, but is actually placed on a separate btrfs subvolume, so I suspected the recursive search upwards was failing to cross the filesystem boundary. Moving the file into the subvolume worked, but out of curiosity I searched through the issues, PRs, and source relating to config file search, and found that fs::canonicalize was being called on the current directory path before starting the search, which means that it will not respect what you see as the directory you are in if you arrived there through symlinks. Given the clear function of canonicalize, I expect this to be intentional, but is it? And if so, why?

(also, this my first time submitting an issue, so any feedback on the format is welcome)

Read libsyntax/src/config.rs around line 390, focusing on the fs::canonicalize call before configuration search. Reproduce the behavior with a .rustfmt.toml in a symlinked home directory, then determine whether the search should preserve the visible symlink path or whether the existing behavior needs explanation.