The new way
As noted in this comment below, the way originally documented in this article no longer applies.
You now need a clone of the separate "git-manpages" repo at the same level as your "git.git" clone. For an example showing how the install works in this case, see "Installing Git 1.7.10 on CentOS 5.7".
The old way
$ cd path/to/your/clone/of/the/official/git.git/repo $ make quick-install-man $ make quick-install-html
This is considerably easier than building the documentation yourself.
Note: This only works from inside a clone of the "git.git" repository, because it works by grabbing the docs from the other branches in the repository. It won’t work if run from inside a downloaded tarball of the source tree.