FTBFS against SWIG 4

[Lucas Kanashiro]

While trying to rebuild src:subversion against Ruby 2.7 I figured out it actually FTBFS due to the swig update to version 4. This is a known upstream bug [1], and the fix was not released yet. This is part of the build log (focal-proposed needs to be enabled to reproduce it):

...
Wrote subversion/bindings/swig/proxy/swig_python_external_runtime.swg
/usr/bin/swig -I/<<PKGBUILDDIR>>/BUILD/subversion -I/<<PKGBUILDDIR>>/subversion/include -I/<<PKGBUILDDIR>>/subversion/bindings/swig -I/<<PKGBUILDDIR>>/subversion/bindings/swig/include -I/<<PKGBUILDDIR>>/subversion/bindings/swig/proxy -I/<<PKGBUILDDIR>>/BUILD/subversion/bindings/swig/proxy -I/usr/include/apr-1.0 -I/usr/include/apr-1.0 -I/usr/include -python -classic -o subversion/bindings/swig/python/core.c /<<PKGBUILDDIR>>/subversion/bindings/swig/core.i
Deprecated command line option: -classic. This option is no longer supported.
make[1]: *** [/<<PKGBUILDDIR>>/build-outputs.mk:290: subversion/bindings/swig/python/core.c] Error 1
make[1]: Leaving directory '/<<PKGBUILDDIR>>/BUILD'
make: *** [debian/rules:228: debian/stamp-build-arch] Error 2
dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2

After a discussion with doko on #ubuntu-devel we brought up with 2 options:

1) Drop the needed bindings. We'd need to take care with the reverse dependencies if we take this route.
2) Maintain a swig 3 source package to support those bindings.

I'd go for the first option, IMO it'd make the future maintenance easier.

[1] https://issues.apache.org/jira/browse/SVN-4818

[Lucas Kanashiro (lucaskanashiro)]

There is a discussion in Debian about it [1], and the maintainer decided to wait for the next upstream release because the current upstream fix requires many changes in the source code.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=951893

[Dimitri John Ledkov (xnox)]

Currently forced the build with swig3.0, however we should remove swig3.0 before focal release as it is hanging onto the archive as an NBS at the moment.

[Lucas Kanashiro (lucaskanashiro)]

I forwarded the changes added by Dimitri to Debian and the maintainer accepted it while subversion does not support SWIG 4 upstream:

https://tracker.debian.org/news/1111658/accepted-subversion-1130-3-source-into-unstable/