is git the right tool for getting package definitions?

[Adam]

(original message was formatted in rich text, so I decided to resend
it in plain text)
Hi guix!
Recently I used nixos on one of my machines. And I noticed people
there use tar balls for fetching package definitions. And It worked
much faster for me.
That was surprising and I decided to write this letter.
Is git the right tool for getting new package definitions? What if git
commits history will become enormous?
As I see, the first guix pull is running too long for a lot of people.
Probably, there are ways to cache all of this.
Anyway, I'm just curious about it. If there are already answers for my
question, I would like to read them.