[Stratoscope]

I'm sure you know this, but for anyone who is new to Unity, one thing that helps a tiny bit is to open the Edit/Project Settings/Editor panel and change the Asset Serialization Mode to Force Text. Then your .unity scene files and such will be text files instead of binary. Whenever I start a new Unity project I flip this setting right away and save the empty project with text assets as the first commit.

This won't solve the problem at all - the asset files are still fairly inscrutable and the slightest change in the editor can result in all kinds of seemingly unrelated changes - but at least you'll have text diffs instead of huge binary files in the repo.