Rename `-targetSHA` to `-SHA` for better polymorphism.
First sketch of temporary references.
Build API.
Leftover.
Use asserts.
Docs.
Remove property — it's in the superclass already.
Style + capitalization.
Make `-deleteWithError:` assert too.
Make `-initWithRepository:` the designated initialized.
Gotta love unexpected recursion.
Add a `repository` parameter because target resolution needs it.
Update GTReference temporary initializer.

Don't get me started on why I didn't get **errors** while building...
Merge branch 'temp-references' into checkout
Use a reference directly.