What about making side tags easily
available to packagers directly? I could build my package that
includes an ABI breaking update and rebuild the dependencies
within that side tag and then submit when everything is
complete.
+1
Maybe something like 'fedpkg build --side-tag=pkgname-abichange',
that would mean to build that package using all packages already
with the same side tag and tag the build with side-tag.
After all the packages are rebuilt, a simple command like 'fedpkg
enable side-tag' will push all the packages with side-tag to
testing.