This file is not yet operational.  Eventually it should record all changes.
Till then, you are advised to resort to our git server where all changes are
logged.  This is how to get anonymous read-only access:
$ git clone git://www.ginac.de/ginac.git ginac
$ cd ginac; git whatchanged
Alternatively you can browse the repository on-line at
http://www.ginac.de/ginac.git