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

[Dmitry Gutov]

On 05/10/2023 19:19, Spencer Baugh wrote:
> > Could you mention which code calls 'registered' on a directory,
> > though? If it's in-tree, that's probably a bug too.
> vc-root-diff.  Here's the trace:
>
> * vc-hg-registered("~/test-hg-repos/empty/")
>    apply(vc-hg-registered "~/test-hg-repos/empty/")
>    vc-call-backend(Hg registered "~/test-hg-repos/empty/")
>    #f(compiled-function (b) #<bytecode -0x10c889a4506dd5b1>)(Hg)
>    mapc(#f(compiled-function (b) #<bytecode -0x10c889a4506dd5b1>) (FE RCS CVS 
> SVN SCCS SRC Bzr Git Hg))
>    vc-registered("~/test-hg-repos/empty/")
>    vc-backend("~/test-hg-repos/empty/")
>    vc-working-revision("~/test-hg-repos/empty/")
>    vc-root-diff(nil t)
>    funcall-interactively(vc-root-diff nil t)
>    call-interactively(vc-root-diff nil nil)
>    command-execute(vc-root-diff)

Huh, it actually looks like that call is unnecessary (the result is 
unused). These lines just come from 2009, mostly unchanged:

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index d3e53858c16..e3b1f7fafda 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -2086,7 +2086,7 @@ vc-root-diff
     (vc-maybe-buffer-sync not-urgent)
     (let ((backend (vc-deduce-backend))
          (default-directory default-directory)
-         rootdir working-revision)
+         rootdir)
       (if backend
          (setq rootdir (vc-call-backend backend 'root default-directory))
        (setq rootdir (read-directory-name "Directory for VC root-diff: "))
@@ -2094,14 +2094,13 @@ vc-root-diff
        (if backend
            (setq default-directory rootdir)
          (error "Directory is not version controlled")))
-      (setq working-revision (vc-working-revision rootdir))
       ;; relative to it.  Bind default-directory to the root directory
       ;; here, this way the *vc-diff* buffer is setup correctly, so
       ;; relative file names work.
       (let ((default-directory rootdir))
         (vc-diff-internal
-         t (list backend (list rootdir) working-revision) nil nil
+         t (list backend (list rootdir)) nil nil
          (called-interactively-p 'interactive))))))

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