Use branch names rather than 'upstream' & 'local'

[christoomey]

Upstream and local are confusing.

I've found that during a rebase, .git/rebase-apply/head-name is the local branch name, but I can't seem to find a reference to what the upstream (typically master) is.

@calebthompson, any thoughts on how I could determine the branch names during while in conflict mode?

[JESii]

'upstream' and 'local' are great for my purposes -- they're prefectly clear for my normal use case. What would be nice would be a commend to get the branch names if that's required, but I can still find that with the commit hash that's displayed in the working split.

Thanks again for a great plugin... use it all the time.