Isn't that the problem that version control has solved? Once the first commit is done you're just uploading deltas/changesets, so the size of the project doesn't really matter.
And you often have more than one change at a time.
As for two gigabytes not being much I don't think their repos is that small. Most of us would properly have no issue downloading it, but you have to upload them (and DSL isn't symetric) and you have to find some place that is willing to host those gigantic repositories.