I wanted to give some kudos to the comment that mentioned CTRL + Z as an option. At the end of the day, it's going to depend on what system that you have Git installed on and what program is configured to open text files (e.g. less vs. vim). CTRL + Z works for vim on Windows.
If you're using Git in a Windows environment, there are some quirks. Just helps to know what they are. (i.e. Notepad vs. Nano, etc.).