Let's encrypt lets you to get https for your website for completely free. It's the easiest way to get SSL certificate free of cost which will be recognized by major browsers. This tutorial goes through the steps that need to be done to get and setup a free SSL certificate for your shared Cpanel hosting. Even though we are talking about Cpanel, it's not exclusively only for Cpanel users, the way described here to get the certificate will work for other cases too if the required conditions are met (which are necessary in all cases).
Git is a version control system. It can be used to manage and maintain websites which gives much more control and efficiency over other manual methods (like using Filezilla and other tools). It's feature rich and the time consumption for upload is super low compared to other non-git equivalent methods.
Tutorials for the tool letsacme which simplifies the task of getting free SSL/TLS certificate from Let's Encrypt.
This is a step by step process on how you can automate getting and installing Let's Encrypt SSL/TLS certificate.