With Tortoise Git the GUI is very efficient when you are typing the commit text.

For example:

https://community.atlassian.com/t5/image/serverpage/image-id/181626i8711D63C554D02DF/image-size/large?v=v2&px=999

As you type the name of a file included in the commit it is offered in a droplist. I miss this feature in SourceTree.