Merge branch 'ef/checkout-empty' into maint

Running "git checkout" on an unborn branch used to corrupt HEAD (regression in 1.7.10); this makes it error out. By Erik Faye-Lund * ef/checkout-empty: checkout: do not corrupt HEAD on empty repo

Junio C Hamano committed May 14, 2012 at 11:42 UTC 3734dbc4abce39c20530e36c2d47d3269ac0e6cd

No changes.