mercurial news: fix extension?

[Uwe Brauer]

Hi

I just read in 

https://www.mercurial-scm.org/wiki/WhatsNew


6.5.4. fix extension

Allows to rewrite file content in changesets or working copy. For
example, automatically applying formatting fixes to modified lines of
code. This experimental extension is now distributed with Mercurial.


I would like to try out that extension without installing the latest hg
stable, since it does not work for me with the hg-git extension.

Does somebody has a pointer?

Thanks 

Uwe Brauer