Add an ArchiveX header

[nim-nim]

Right now rpm assumes it can scrap the archivex filename from SourceX, but nowadays many upstreams publish source archives on URLs that do not contain the actual archive name*

The common workaround is to change SourceX to url#/archivex filename, but that is quite confusing to new packagers and creates artificial urls which are very hard to parse and maintain, are error-prone, have the risk that the website will interpret them differently from rpm

rpm should bite the bullet and allow for each SourceX an optional corresponding ArchiveX, with the following semantics:

1. if archiveX exists set the filename of SourceX to archiveX
2. if it does not scrap the filename of SourceX the same way it's done today

[ffesti]

This is a valid use case. But I dislike the idea of adding a new tag for this. I'd rather like to see something that is closer to the hack without its drawbacks
Source1: https://foo.bar/baz -> ba-1.2.tgz or
Source1: https://foo.bar/baz : ba-1.2.tgz

[nim-nim]

While anything would be better than the current situation, from a rpm user POW, I'd like less magic and special things in rpm, and more generic operators and constructs.

IE, everything is a variable, except for things that need multiple declarations, and use tags.

SourceX as a tag is IMHO a mistake, for example. You'll never need to declare it multiple time, since you need a unique name to attach special setup actions to. So special tag + special operator does not improve things a lot.

Generic constructs help automating a lot, special constructs need special handling, that always neem to hit corner cases.

So as a long term direction, I'd like unique name tags to be slowly deprecated and replaced by unique name variables with generic variable set/unset behaviour.

And, for Tags that can not be converted to variables right now, because they need the multiple declaration property, I’d like rpm to grow generic multi-declaration primitives.

1. for Tags that are multi-declared as a poor man way to create arrays: add real rpm variable arrays (%set array [a,b,c], %append array [d,e], %array %= [a,b,c], %array %+= [d,e])
   RFE: Add variable arrays to rpm #1149

2. for Tags that multi-declared as part of a subpackage scope: create a real %{scope(subpackage): } primitive (that’s just a generalisation of the -n used by %package, %description, %files, etc, except without needing a separate flag per line, and without all the bugs when you cut and paste and forget to change the -n value on one of the lines)
   RFE: add variable named scoping to rpm #1150

[kadler]

This is a valid use case. But I dislike the idea of adding a new tag for this. I'd rather like to see something that is closer to the hack without its drawbacks
Source1: https://foo.bar/baz -> ba-1.2.tgz or
Source1: https://foo.bar/baz : ba-1.2.tgz

I definitely like this better than having a separate "ArchiveX" tag to correlate things.