External changelog integration

[pmatilai]

Pretty much all distros have at least the option of pulling the spec changelog from an external source - namely the package SCM (dist-git in the Fedora world). There have been various suggestions to make rpm better integrate with this, such as

• Extend %changelog to accept filename. #393
• implement rpmbuild --changelog=FILE support #69

...and I think a whole other bunch in RH bugzilla and other ticket systems over time, yet here we still are, none of them have been implemented/applied, because the designs just haven't seemed right. If you have an external process to do 'git log > changes; rpmbuild --changelog=changes foo.spec' then that same process can could just as easily append the changes to the spec itself. Plus it's a step you need to remember to do manually unless you have extra tooling around rpmbuild. Adding -f support to %changelog to allow for an external changelog forces silly '%changelog -f somefile' boilerplate in each and every spec, and worse, introduces a whole new world of spec parse failures because the externally generated file is not there.

To come up with a solution that satisfies most if not everybody, we need to be aware of what people are currently doing. I don't know what exactly other distros do (just append to the spec or something fancier? please fill us in), in Fedora there's rpmautospec to fill this role and (optionally) generate a release automatically too. I haven't used it beyond curiosity testing a bit. There are interesting ideas in there, but then it also requires running some external wrapper tooling to make it actually work. And at that point we're back to: if external tooling is required, then what do we need rpm changes for? This is already possible, in numerous different ways. But surely, there must be something we can do in this area.

Thoughts and ideas, even wacky ones, welcome. It's better to hash out the ideas as a central discussion that speculate independent RFE tickets. We'll file ticket(s) if/when some conclusions are reached.

I've been recently working on #1087, and one thing that will give us is a way to automatically populate spec sections with macros. This should make it possible to invoke something like %([ -d .git ] && git log --pretty="* %ad %an <%ae>%n- %s%n") (real-worl will want more complicated "filter" there now doubt) to autofill %changelog from inside rpmbuild itself with no need for external commands and zero changes to the spec itself. Except to trim out the %changelog section entirely. Whether this kinda of thing is useful to anybody at this point is another question.

[voxik]

Can the %changelog section being made similar to others, such as %prep, %build, etc? Thinking of this, can %files section be more similar to those as well 🤔

[pmatilai]

I don't know what you mean by that. %prep, %build, %install etc are shell scripts, %files and %changelogs are static data that rpm parses.

[voxik]

So if they were scripts, the output of the script could be used as changelog / file list

[pmatilai]

They're not scripts, and will not become such, it makes no sense really. For script generated files section there's already -f. The difference to %changelog is that a changelog is not a build result, it's something that exists before it. It's also possible to use the dynamic spec generation facility to produce those as much as any other section.

I'm not looking for per-package hacks but a generic integration with external changelogs.