CVSTrac source uses two spaces for indentation, no tabs. Spaces for indentation is more typical of Emacs, rather than vi.
In order to edit CVSTrac source with vi, you'll want the following options defined:
:set expandtab :set tabstop=2 :set shiftwidth=2
for convenience, a .vimrc file is provided in the CVSTrac source which does precisely this. In order to use it, you need to
in ~/.exrc or ~/.vimrc. Note that the exrc option is a potential security risk since .vimrc files can run shell scripts and such. Know and trust your source before enabling this.