[build2] Set RPM epoch

[Paul Stath]

Hi Boris,

The code comment block you cite is in the generated documentation section "7.2.2 Fedora Package Mapping for Production".
Under the following paragraph:
 "Let's start with the case where neither distribution (fedora-version) nor upstream
  version (upstream-version) is specified and we need to derive everything from the
   bpkg version (what follows is as much description as rationale)."

I had expected that since the distribution specific (fedora-version) attribute was
being set that this logic would not apply and the <epoch> "So we shift this value range" logic would not apply.

Please note that the text in the cited code block does not exactly match the generated
documentation for the build2 0.17.0 version that I am using.

> So try `fedora-version: 2:1.2.3`.
I tried this as well, hoping that "Epoch: 1" would show up in the RPM spec file, but it didn't seem to make any difference.
The "Epoch:" in the spec file is still not being set.

Any other suggestions or debugging that I can do?
I set "bindist --verbose 6" in the hopes it might provide a clue, but I didn't see anything helpful.

I suppose in the very short term, I could use the bindist "--fedora-prepare-only" argument
and add the "Epoch: 1" to the generated RPM spec before running the rpmbuild commands.

> We could probably support something like 1:$ with a bit of effort so feel free
> to file an issue for that.
That would be great.   I will make a feature request.

Since the order of "version" and "fedora-version" in the package manifest file
does not matter, for now I can place them on adjacent lines to make it
more likely that they will get changed at the same time.

version: 1.2.3
fedora-version: 1:1.2.3

Best regards

----
Paul Stath
Principal Systems Engineer
JMA Wireless
pstats at jmawireless.com



> -----Original Message-----
> From: Boris Kolpackov <boris at codesynthesis.com>
> Sent: Wednesday, June 4, 2025 8:28 AM
> To: build2 toolchain mailing list <users at build2.org>
> Cc: Paul Stath <PStath at jmawireless.com>
> Subject: Re: [build2] Set RPM epoch
> 
> Paul Stath via users <users at build2.org> writes:
> 
> > To set the epoch, I added the  "fedora-version" to the project
> > manifest file ("fedora-version: 1:1.2.3") Regenerate the RPM files
> > using the "bpkg bindist -wipe-output -keep-output <project>" command.
> > I expected this to result in the "Epoch:" line being added to the
> > generated spec file, but no such luck.
> 
> This comment from the source code I believe explains why this is:
> 
>     // <epoch>
>     //
>     //   On one hand, if we keep the epoch, it won't necessarily match
>     //   Fedora's native package epoch. But on the other it will allow our
>     //   binary packages from different epochs to co-exist. Seeing that this
>     //   can be easily overridden with a custom distribution version, let's
>     //   keep it.
>     //
>     //   Note that while the Fedora start/default epoch is 0, ours is 1 (we
>     //   use the 0 epoch for stub packages). So we will need to shift this
>     //   value range.
> 
> So try `fedora-version: 2:1.2.3`.
> 
> > Also, can the "fedora-version" attribute in the package manifest file
> > use the bpkg "version"? Since all I want to do is set the epoch of the
> > RPM, is it possible to specify the "fedora-version" attribute in a DRY
> > fashion so that it uses the bpkg "version" ? Something like:
> > "fedora-version: 1:$version"   or "fedora-version: 1:"
> 
> No, not quite. The details are here:
> 
> https://build2.org/bpkg/doc/build2-package-manager-
> manual.xhtml#manifest-package-distribution
> 
> We could probably support something like 1:$ with a bit of effort so feel free
> to file an issue for that.