Copyright-holder and year information is extracted from git log.
git history begins in 2005. So (C) from 1998..2005 is lost. Also some
(C) assignment of commits where the committer didn't use --author.
Also push the increasingly unwieldly paste parameters into a context object.
As with othe things, currently it is only possible to do "cross-type paste" by
explicitly selecting the target track. We will need to get automation region
view selection working to do better here, but at least for now it's possible to
get the data over.