From that page:
$ git clone git://git.gnome.org/glib
$ cd glib
$ git co 2.26.1
>> git: 'co' is not a git command ...
$ ./autogen.sh --prefix=/opt/lib/glib2.26
>> is it glib2.26 or glib that should be used? earlier it looks like glib...
$ sudo make install
>> Also, everything in /glib says 2.0. Thanks for the help, but that's not the clearest answer.