new vc rcs file checkin problem with tramp

[Ville Skyttä]

On Thursday 27 September 2007, you wrote:
> Ville Skyttä <scop at xemacs.org> writes:
> > But in the absence of process-file or similar that we could use the tramp
> > handlers for, let's leave tramp as is (patched) and go all the way then
> > in vc - the attached patch is not that pretty but I think it should fix
> > this issue.  Could you test it?
>
> Sorry to enter your discussion.

You're very much welcome, I'm glad you did!

> But I believe it is not a good idea to 
> have tramp-related code in vc*.el. In order to hide such dependencies,
> tramp-vc.el was introduced.

I see and agree.  And I did mention that my patch wasn't pretty ;)

> And indeed,
> `tramp-send-command-and-check' has a different parameter list in Tramp
> 2.1. And since Tramp 2.1 is also intended for XEmacs, your patch would
> fail there already.

Thanks for the info.

> >  (defun vc-user-login-name (file)
> >    "Return the name under which the user accesses the given FILE."
> >    (or (and (eq (string-match tramp-file-name-regexp file) 0)
>
> Hmm. In GNU Emacs (please forgive me) the function `file-remote-p'
> supports file name handlers for magic file names. Such a call is much
> more robust wrt Tramp internals.

The code above comes as-is from GNU Emacs at the point I last synced it which 
was somewhere before it went GPLv3 - I haven't looked at later versions there 
because I think we're not ready to receive GPLv3 code in XEmacs yet.

> (or (functionp 'process-file)
>     (defalias  'process-file 'tramp-handle-process-file))
>
> The other altrnative would be to call `tramp-handle-process-file' directly.

This was the first approach I tried.  However, it doesn't work for me, 
evaluating (vc-user-login-name "/[some.host]foo/bar") I get this:

Debugger entered--Lisp error: (wrong-type-argument number-char-or-marker-p 
nil)
vc-user-login-name("/[some.host]foo/bar")
eval((vc-user-login-name "/[some.host]foo/bar"))
eval-interactive((vc-user-login-name "/[some.host]foo/bar"))
eval-last-sexp(t)
#<compiled-function nil "...(13)" [standard-output terpri eval-last-sexp t] 2 
1250159 nil>()
call-interactively(eval-print-last-sexp)

I'm not familiar with tramp and not quite sure how tramp-handle-process-file 
is supposed to work - it appears to return what shell-command returns (nil 
for my test cases? dunno - not documented) and that value is fed to zerop in 
vc-user-login-name.  I gather shell-command is wrapped by tramp's handler in 
GNU Emacs so it could be different, but in XEmacs we get the usual unwrapped 
shell-command which doesn't seem fit for this purpose.

Implementing process-file and the handler infrastructure would look like a 
welcome addition, but it's much more work than I personally have time for at 
the moment and probably would only work for bleeding edge XEmacs.  And that's 
a no go because the packages tree needs to work with earlier stable XEmacs 
branches too for which largish feature work such as this is not generally 
welcome.

I also briefly tried the old defadvice way by reverting the patch I posted to 
tramp.el earlier, but couldn't get that to work either (I'm not sure about 
the details but it could have been that I missed something I should have 
changed in vc-hooks.el too).

If you have other ideas how to get around this, I'd be glad to hear about 
them.