Hi,

Windows 7
GNU Emacs 26.0.50 (build 1, x86_64-w64-mingw32) of 2017-08-27
(backup-by-copying t)

When I tramp to a host (linux) and edit a file, and save it, I get an error
about the backup as below. The ACL is in different format on Linus and on
Windows. It is "user::..." on linux, however, it looks like "O:S-1-5-21-"
on windows.

Could we allow the user to set whether to copy ACl for certain type of
files?

Debugger entered--Lisp error: (file-error "Converting ACL" "Invalid
argument"
"c:/Users/user/HOME/.emacs.d/autosave/Rfiles/!drive_c!plink!!user@host
!!!path!user!Ava!_mortality.R.~1~")

set-file-acl("c:/Users/user/HOME/.emacs.d/autosave/Rfiles/!drive_c!plink!!user@host!!!path!user!Ava!_mortality.R.~1~"
"user::rw-\ngroup::rw-\nother::r--\n")

set-file-extended-attributes("c:/Users/user/HOME/.emacs.d/autosave/Rfiles/!drive_c!plink!!user@host!!!path!user!Ava!_mortality.R.~1~"
((acl . "user::rw-\ngroup::rw-\nother::r--\n") (selinux-context nil nil nil
nil)))
  backup-buffer-copy("/plink:user@host:/path/user/Ava/_mortality.R"
"c:/Users/user/HOME/.emacs.d/autosave/Rfiles/!drive_c!plink!!user@host!!!path!user!Ava!_mortality.R.~1~"
436 ((acl . "user::rw-\ngroup::rw-\nother::r--\n") (selinux-context nil nil
nil nil)))
  backup-buffer()
  basic-save-buffer-2()
  basic-save-buffer-1()
  basic-save-buffer(t)
  save-buffer(1)
  funcall-interactively(save-buffer 1)
  call-interactively(save-buffer nil nil)
  command-execute(save-buffer)

Best Regards,
Shuguang