Support for multiple installed versions of a program.

[Rob Browning]

[ In summary of what's below, I'm asking asking if there's upstream
  interest in trying to get info pages to handle the installation of
  multiple versions of a given program gracefully. ]

I hope I have the right list, and I hope this hasn't already been
discussed to death.  If either is false, just let me know.

Debian/GNU tries to arrange things so that when useful, people can
have more than one version of a given program installed at the same
time.  For example, we allow you to install xemacs21, emacs20, and
emacs21 all at the same time, and we support installing a separate
gnus package (with the latest gnus) alongside all of these [1].

Generally we support direct invocation of a given version of a program
via something like "/usr/bin/emacs21" and invocation the system
default (administrator adjustable) version via "/usr/bin/emacs", the
latter of which is controlled by Debian's update-alternatives
mechanism.  update-alternatives also controls which manpages are
associated with "man emacs" in this case.

So far we've successfully resolved essentially all the details
involved in allowing multiple-versions to coexist, save one: the
handling of info pages -- and accordingly there are a whole raft of
bugs, some *very* old, filed against the various emacsen,
emacsen-common, gnus, etc. all concerned with the accessibility of the
info pages.

Though we've tried to figure out ways we could handle this locally, it
seems like without upstream support, we're not likely to have a very
clean solution.  So has any thought been given to this issue, and is
this even something you'd be interested in trying to address?

It seems like fixing this might require, at least, some enhancements
to the various info browsers, and to the semantics and syntax of
cross-references, though perhaps there's already some way we can
handle this that we haven't thought of yet...

In any case, here's one of the bugs discussing the issue.
<http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=130653&repeatmerged=yes>
See the end of the log for a part of the solution we've considered.
Manoj, in particular has thought quite a bit about this.

Thanks

[1] I'm also planning to add support for multiple versions of guile
    soon.

-- 
Rob Browning
rlb @defaultvalue.org, @linuxdevel.com, and @debian.org
Previously @cs.utexas.edu
GPG=1C58 8B2C FB5E 3F64 EA5C  64AE 78FE E5FE F0CB A0AD