shadowfile.el reloaded

[Michael Albinus]

Hi,

shadowfile.el is implemented with Ange-FTP in mind. It uses a lot of
Ange-FTP internal functions and data structures.

Since Tramp has been integrated into Emacs 22, this doesn't work
well. Bug#4526 and bug#4846 speak about. One could do some variable
fiddlings to let it work (setting `tramp-default-method' to "ftp"), but
this is not the way we want to go.

With Emacs 26, Tramp syntax has been changed. shadowfile.el doesn't work
any longer even with the tricks.

So I have rewritten it, to use Tramp instead of Ange-FTP. There are a
lot of incompatible changes I had to decide for, but this couldn't be
avoided.

I would like to install it into the emacs-26 branch, because one could
regard this as bug fixing related to the changed Tramp syntax in Emacs 26.

Well, I'm not a shadowfile.el user, so this would require more testing
from other users. But at least I have written shadowfile-tests.el in
parallel, which should give us a minimal level of trust.

Comments?

Best regards, Michael.