checkout: updates to tracking report

checkout: updates to tracking report

Ask branch_get() for the new branch explicitly instead of
letting it return a potentially stale information.

Tighten the logic to find the tracking branch to deal better
with misconfigured repositories (i.e. branch.*.merge can exist
but it may not have a refspec that fetches to .it)

Also fixes grammar in a message, as pointed out by Jeff King.

The function is about reporting and not automatically
fast-forwarding to the upstream, so stop calling it
"adjust-to".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Daniel Barkalow <barkalow@iabervon.org>