xmllint and paragraph line width

Hi Everyone,

We run our book source through xmllint before making the book and
checking in sources to version control.

We would like to format the sources so paragraphs have a break at 80
or 90 chracters. The line breaks make it easier on version control
tools like Git, and make it easier to see changes and the end of a
sentence (that would otherwise require scrolling).

It looks like xmllint does not have the formatting option. I'm
guessing I am missing an obvious step, like using some other tool to
apply the line breaks.

How do we format paragraphs to a particular width when using xmllint
in our toolchain?

Thanks in advance.