Two questions about making rpms work on multiple OS versions

["Axel Liljencrantz" <liljencrantz gmail com>]

Hi,

I am trying to make a spec file for a commandline shell
(http://roo.no-ip.org/fish) that works on multiple OS versions as well
as different OS:es.

I have run into two separate problems:

* Changing package names. To build fish, the X headers are required.
The name of the package providing these have changed from
XFree86-devel to xorg-devel to libX11-devel, and that is only on
Fedora. The location of the files in the filesystem have changed as
well, since Fedora Core 5 puts X stuff in /usr, not /usr/X11R6. Is
there some way to specify something like conditional dependencise that
allows you to depend on _one_ of several packages? I realise that this
could be solved with virtual packages, but since I can't update the X
packages for all the RPM-using distros in the world, that is no help
whatsoever. Without this, I can't upload one fish rpm to fedora extras
that gets built for all fedora versions.

* Overzelous dependencies. When building fish on Fedora Core 5, a
dependency on libc.so.6 is automatically added, but fish works just
fine using earlier versions of libc. How can one specify that fish
doesn't actually need the latest version of a library? Doing so would
enable me to provide an rpm on the fish download page that works with
any semi-modern RPM-based distribution.

Sorry if either of these questions has been answered elsewhere, I
looked in the maximum RPM online book and seartched the archive of
this list, to no avail.

--
Axel