getting git to ignore modifications to specific files

[Chris Packham <judge.packham@gmail.com>]

Hi,

We have a git repository that as some GNU build system (a.k.a.
autotools) files, my current problem is with the INSTALL file but I
suspect there may be some others. These can get modified if you are
running a different version of autotools from when the files were created.

I've had various arguments about which autotools files should or
shouldn't be included in our repositories. My general rule of thumb is
that if it is automatically generated then it shouldn't go into the
repository.

There are a couple of repositories that are local clones of 3rd party
repositories which have included the pesky auto-generated files so whle
I can remove the offending files from repositories we control I need
another solution for the 3rd part ones.

I did a bit of googling and found
  git update-index --assume-unchanged

Which works locally to stop git status from complaining. Is there anyway
for me to make a change to our clone (a .gitattribues entry?) so that
everyone can get this by default?

Thanks,
Chris