Documentation is missing pygit2 install from repository checkout instructions

The Advanced installation instructions don't provide any guidance on installing pygit2 from a repository checkout.

There are instructions for installing libgit2 but then for pygit2 it only says the following:

Now install pygit2, and then verify it is correctly installed:
$ pip install pygit2

This will install the latest released version but not a version checked out from the repository.

Looking at what is provided in the Makefile the following is a reasonable guess and seems to work

cd pygit2
sudo python install

or in my case sudo python3 install.

It would be helpful if the documentation contained some verification that this is recommended method when installing from a repository checkout.

从高级安装说明和仓库的 Makefile 开始。比较现有的 libgit2 和 pygit2 安装步骤，记录从仓库 checkout 安装 pygit2 的受支持方式，并包括对已安装 checkout 版本的验证。