a: always yes (yes to this question and all others)
x: exit
d: show the differences between the old and the new file
h: help, list all options
Notes :
If you don't remember this definitions you can always enter h and see the list.
Also in the new version, when you enter one of the letters you will see the definition showing behind the question so that you can verify your answer before pressing Enter key.
The one in uppercase is the default one. If that is your choice, you can just hit enter.
I've listed some useful videos that would be beneficial for beginners or some one who wants to understand software testing from
scratch. These are free and best videos that I found on YouTube.
You can watch these in sequence. The first three videos discusses the fundamental and the 4th and 5th playlist has the information in depth.