bug#2912: 23.0.92; Ediff over TRAMP too slow

[Michael Albinus <michael.albinus@gmx.de>]

David Abrahams <dave@boostpro.com> writes:

> Ediff two remote files using /ssh:... protocol
>
> It seems to go over the network for everything.  At first I thought it
> was the auto-refining, but I turned that off and it didn't seem to make
> any difference in speed.

In case of remote files, ediff compares local copies, indeed. I'm not so
familiar with ediff, therefore I don't know, whether this can be changed
easily, running the diff command on the remote host. However, this
introduces more complexity into ediff: there might be protocols which do
not support execution of remote commands (like ftp or smb). Furthermore,
ediff would need to check, whether the files to be compared reside on
the same remote host.

I don't believe that this shall be changed before the release of Emacs
23.1. After the release, it might be a new feature somebody (with more
skills than I have on ediff) might implement.

For larger files, I recommend to use the scp method instead of ssh.

Best regards, Michael.