Merge branch 'jc/checkout-detach-wo-tracking-report'

"git checkout/switch --detach foo", after switching to the detached
HEAD state, gave the tracking information for the 'foo' branch,
which was pointless.

Tested-by: M Hickford <redacted>
cf. <redacted>

* jc/checkout-detach-wo-tracking-report:
  checkout: omit "tracking" information on a detached HEAD

diff --cc builtin/checkout.c
Simple merge