bug#66364: 29.1.50; vc-hg-registered/state are slow on directories of large repos

[Dmitry Gutov <dmitry@gutov.dev>]

On 05/10/2023 18:36, Spencer Baugh wrote:
>  From 5573b678f816f81623deb7ebde66dfd3ebe92355 Mon Sep 17 00:00:00 2001
> From: Spencer Baugh<sbaugh@janestreet.com>
> Date: Thu, 5 Oct 2023 11:35:25 -0400
> Subject: [PATCH] Optimize vc-hg-state for directories
> 
> Directories are never tracked in hg, so it's pointless to run
> vc-hg-state on them.  And, in fact, our implementation previously
> would list all the files contained in the directory and then parse
> that in Emacs, which is very slow in large repos.
> 
> Let's just use the knowledge that directories aren't tracked in hg,
> and skip running hg entirely.
> 
> * lisp/vc/vc-hg.el (vc-hg-state): Return unregistered for directories.
> ---
>   lisp/vc/vc-hg.el | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/lisp/vc/vc-hg.el b/lisp/vc/vc-hg.el
> index c3e563a1f10..9a30706f519 100644
> --- a/lisp/vc/vc-hg.el
> +++ b/lisp/vc/vc-hg.el
> @@ -216,8 +216,10 @@ vc-hg-registered
>   
>   (defun vc-hg-state (file)
>     "Hg-specific version of `vc-state'."
> -  (let ((state (vc-hg-state-fast file)))
> -    (if (eq state 'unsupported) (vc-hg-state-slow file) state)))
> +  (if (file-directory-p file)
> +      'unregistered
> +    (let ((state (vc-hg-state-fast file)))
> +      (if (eq state 'unsupported) (vc-hg-state-slow file) state))))
>   
>   (defun vc-hg-state-slow (file)
>     "Determine status of FILE by running hg."

Perhaps we should just follow the example of vc-git-registered and 
return nil.

Could you mention which code calls 'registered' on a directory, though? 
If it's in-tree, that's probably a bug too.