How is the skillset of an evolution being chosen?

You may already know that if you catch two Pidgeys, they may have a different skillset.

I've also seen that evolving them from different skillsets will also create Pidgeottos with different skillsets.

Are those skills chosen randomly or do they follow a specific pattern? (Like Pidgey pattern 1 will always evolve into Pidgeotto pattern 1.)

If they are specific, is there a website to check for them?

I found a reddit post that lists special moves but the top comment asks about move correlation: https://www.reddit.com/r/TheSilphRoad/comments/4sqqb0/movesmovesets_in_pokemon_go_an_almost_complete/

One of the comments provided a chart that illustrates the moves a pidgey learns when evolved into a pidgeotto: http://i.imgur.com/Nn6dMq6.png

It shows that there is no 100% correlation at all between movesets from one evolution to another. If there is a ratio at all between moves I cannot say for sure due to the small sample size given.