As SaaS admin you can access the changelogs of your blends and templates via the SaaS API.
If you use the SaaS API connector you could create a blend in your admin account to get the (latest) changelog of you template and store it in the version control tool of choice, like Github.
Build a blend in the 'my blends' section of your admin account
Connect the SaaS API connector with your own credentials (my account > API)
Get the right templates of blends via the 'list blends in account' or 'list templates' blocks
Access the changelogs via the 'List Blend Change Log (incrementally)' block
You can specify the 'blocks' property to only get the workflow information
Send the information to Github with the Github block 'Generic create'.
please note you will need to encode the change log 'blocks' properties to a json format by using the formula 'Object'