[Q] Mark files for later commit?

Hi folks!

I just hit into an situation where a certain file contains a human
written changelog, which is modified (not prepended) for each single
commit in the project, is being committed along with the actual patch.

This approach makes it very difficult to backport the commits, since
it will always try patching the changelog file as well.

The changelog is only supposed to be committed at new releases, but is
kept maintained continuously so stuff won't be forgotten.

So this makes me wonder, is there a way to mark certain files for
being committed later on? Which does not automatically get added to
the staging area (on "git commit -a" or "git add ." and so on) unless
it's specifically mentioned by "git add"?

We've discussed making it generated automatically, but that's not as
easy as it may sound.

How would you like a git feature like described above, marking files
for later inclusion?

Thanks!
--
Daniel