This is the class you are most likely to use if you want to generate a changelog from your own Python script.
samsgeneratechangelog.GenerateChangelog
You will only need to interact with this class if you're creating your own template builder.
samsgeneratechangelog.GitHelper
This is the class from which the file_commits objects in the templates are instantiated. Look here for attributes which you can use directly in your Jinja2 template.
samsgeneratechangelog.FileCommit