O.k.  So a gzipped tarball is kind of comforting to you.  Here is 
one last effort to suggest Subversion (svn):

If you checkout the stable release with svn, a la
  
  svn co http://svn.gna.org/svn/pism/tags/stable0.2 pism0.2

then you can get bug fixes by just doing

$  make update

If you use the .tar.gz then you have to create a new directory 
and think about all the clutter you have already created, and
whether you want to save it.