[libvirt] seek alternative way of compiling historical version

Hi All, To compile to a non-current version, I could download a tar ball, or switch to an older branch in git, then do ./autogen.sh (or ./configure) && make && make install. But for some purpose, I may want to compile to historical version easily without redundantly downloading the source by using some magic flag passed into either ./configure, ./autogen.sh, or make, e.g.: $ ./configure --version=2.0, or $ ./autogen.sh --version-git=1.0 Is that possible at all? Related question, normally speaking, how to test back-compatibility of a new patch, or do we need to test it at all? P.S., I was just reading v0.0.1 libvirt [1]. It is so nice to see there is, well, was nothing more then 2000 LOC for C source code. [1] ftp://libvirt.org/libvirt/old/libvir-0.0.1.tar.gz Dan