Merge branch 'jk/branch-quiet'

Even with "-q"uiet option, "checkout" used to report setting up tracking.
Also "branch" learns "-q"uiet option to squelch informational message.

By Jeff King
* jk/branch-quiet:
teach "git branch" a --quiet option
checkout: suppress tracking message with "-q"

diff --cc Documentation/git-branch.txt
Simple merge

diff --cc builtin/checkout.c
Simple merge