Merge pull request #1827 from aaronraimist/git-prereq

Document `git` as a potential prereq

docs/prerequisites.md

@@ -20,6 +20,8 @@ If your distro runs within an [LXC container](https://linuxcontainers.org/), you
 
 - The [Ansible](http://ansible.com/) program being installed on your own computer. It's used to run this playbook and configures your server for you. Take a look at [our guide about Ansible](ansible.md) for more information, as well as [version requirements](ansible.md#supported-ansible-versions) and alternative ways to run Ansible.
 
+- [`git`](https://git-scm.com/) is the recommended way to download the playbook to your computer. `git` may also be required on the server if you will be [self-building](self-building.md) components.
+
 - An HTTPS-capable web server at the base domain name (`<your-domain>`) which is capable of serving static files. Unless you decide to [Serve the base domain from the Matrix server](configuring-playbook-base-domain-serving.md) or alternatively, to use DNS SRV records for [Server Delegation](howto-server-delegation.md).
 
 - Properly configured DNS records for `<your-domain>` (details in [Configuring DNS](configuring-dns.md)).