bug#54935: 28.1; vc-dir fails with "sort: Wrong type argument: sequencep, t"

[Mike Woolley]

New in Emacs 28.1, vc-dir fails on some of my directories with "sort: Wrong 
type argument: sequencep, t”:

Debugger entered--Lisp error: (wrong-type-argument sequencep t)
  #f(compiled-function (d1 d2) #<bytecode -0xaf17ad190f8dc52>)((Git . "~/") 
(CVS . t))
  sort(((CVS . t)) #f(compiled-function (d1 d2) #<bytecode -0xaf17ad190f8dc52>))
  vc-responsible-backend("/Users/mike/")
  vc-dir("/Users/mike/" nil)
  funcall-interactively(vc-dir "/Users/mike/" nil)
  call-interactively(vc-dir nil nil)
  command-execute(vc-dir)

It’s going wrong trying to take the _length of t_ in the following code in 
vc-responsible-backend:

        ;; Just a single response (or none); use it.
        (if (< (length dirs) 2)
            (caar dirs)
          ;; Several roots; we seem to have one vc inside another's
          ;; directory.  Choose the most specific.
          (caar (sort dirs (lambda (d1 d2)
                             (< (length (cdr d2)) (length (cdr d1))))))))

This scenario was working fine in previous versions of Emacs, so looks like 
recent breakage.

Note that there is a workaround by providing C-u to vc-dir and then manually 
selecting Git, but clearly it would be better if the problem was fixed.

Thanks,
Mike


In GNU Emacs 28.1 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 
Version 10.14.6 (Build 18G95))
 of 2022-04-04 built on builder10-14.lan
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.3.1

Configured using:
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