[scl.org] Setting SCL RPM build options in COPR?

[Nick Coghlan]

On Mon, Sep 18, 2017 at 9:29 PM, Honza Horak <hhorak at redhat.com> wrote:
> On 09/18/2017 07:29 AM, Nick Coghlan wrote:
>> 2. Assuming I haven't missed anything, how do the *default* values for
>> "scl" and "vendorscl" actually get set?
>
> We can kinda control what packages are part of the minimal buildroot for
> every copr or cbs tag -- for SCL case there is the <scl>-build package that
> sets this 'scl' macro. You can add more macros if you like and they will be
> defined at a time a particular SRPM/RPM is built. By that trick and changing
> what macros are defined in <scl>-build, you may basically build more
> variants of a single SRPM and produce different output.

That's what I thought, but I couldn't find anything in sclorg-distgit
that actually *sets* them for the rh-python35 case.

https://github.com/sclorg-distgit/rh-python35/blob/sig-sclo7-rh-python35-rh/macros.additional.rh-python35
has the comment "the @scl@* macros are defined in
macros.python3.python33 in python33-python-devel"

That's presumably referring to
https://github.com/sclorg-distgit/python/blob/sig-sclo7-rh-python35-rh/macros.python3,
which still doesn't *set* "@scl@" or "@vendorscl@", it assumes they're
set somewhere else.

So I'm still confused as to:

- what's up with the "@" symbols in "@scl@" and "@vendorscl@"?
- where can I find an example package that shows how to define them
via a package in the buildroot so I can set up sclo-python-preview
COPR builds?
- where can I find documentation that explains how to do this when you
*can't* pass arbitrary RPM build options?

Cheers,
Nick.

P.S. https://www.softwarecollections.org currently appears to be down
(I noticed when attempting to find docs about this)

-- 
Nick Coghlan
Red Hat Platform Engineering, Brisbane