Conditionally applying a patch based on a program's EVR

[Alan Dunn]

I want to conditionally apply a patch in a spec file based upon the
version of a package. (There's an emacs package that needs a patch to
work with the latest version of xemacs, but this patch shouldn't be
applied for previous versions of xemacs.) I know that for checking
something like Fedora version numbers I can use

%if 0%{?fedora} > 9
...
%endif

but is there an easy way to do this for a version number in say, EVR
form? That is, something like

%if %{program_version} > 1.2.3
...
%endif

(%{program_version} will always be defined)

RPM doesn't seem to support a mechanism like this in %if conditionals
(I believe having a digit first causes rpmbuild to try and interpret
the result as a number), though clearly there is a mechanism for
examining EVRs of this form for other parts of rpmbuild.

One could try something like

%if "%{prorgram_version}" > "1.2.3"

which does string comparison, but this doesn't work for some version
combinations, since, for example, we would want 1.10.1 > 1.9.1

- Alan