How to build libvirt from git on Fedora:

mkdir ~/rpmbuild

(cd ~/rpmbuild && mkdir BUILD BUILDROOT RPMS SOURCES SPECS SRPMS)

git clone git://git.et.redhat.com/libvirt.git

cd libvirt

git checkout -b mystuff

export AUTOBUILD_INSTALL_ROOT=$HOME/builder

./autobuild.sh

The above will clone the tree, checkout a branch to hack on, build and test the code, then generate source and binary RPMS. You’ll also be set then to do local manual builds.

Thanks to danpb for clues.