bug#28156: Emacs quietly munges symlink contents

[Paul Eggert]

Michael Albinus wrote:

> it is Tramp's (almost undocumented) make-symbolic-link
> implementation to handle TARGET as well, and to strip the remote part of
> this. I wouldn't be surprised if existing packages will be broken if we
> change this.

That should not be a problem with the proposed patch, as it does not affect how 
Tramp handles TARGET when making a remote symlink.

> --8<---------------cut here---------------start------------->8---
> M-x make-symbolic-link RET /:~eggert RET /tmp/foo RET
>
> # ls -l /tmp/foo
> lrwxrwxrwx 1 albinus albinus 21 Aug 24 13:19 /tmp/foo -> /home/albinus/~eggert
> --8<---------------cut here---------------end--------------->8---
>
> It is questionable whether "/:~eggert" shall be expanded to
> "/home/albinus/~eggert". I agree with you, that it shouldn't, the target
> shall be just  "~eggert".

Yes, adding support for /: for interactive use sounds reasonable. I updated the 
patch to do that; please see attached.

> For a TARGET which looks like a remote file name, I propose to keep the
> current behaviour (stripping the remote part).

That's fine if LINKNAME is also remote, since symlinks act locally. That is, if 
TARGET and LINKNAME are both remote to the same filesystem, Tramp can continue 
to munge TARGET so that it works on that filesystem. However, Tramp should not 
be in the business of specifying symlink behavior for local symbolic links. It 
should let the OS do that. If LINKNAME is local, TARGET should just act as 
itself without Tramp getting in the way.

> it is just proper file name quoting

The target of a local symbolic link is a string. It need not name a file, and 
often does not name a file. Trying to apply some file name rules to it, and not 
others, is confusing and leads to broken code. For backward compatibility we 
appear to need to handle leading ~ in interactive use and to provide an escape 
for leading ~, but let's not try to inflict these complex rules on code. For 
code, make-symbolic-link should just treat a local target as a string, the way 
the OS does.

0001-Do-not-munge-contents-of-local-symbolic-links.patch
Description: Text Data