Merge branch 'maint-1.6.0' into maint-1.6.1

* maint-1.6.0:
  Documentation: clarify .gitattributes search
  git-checkout.txt: clarify that <branch> applies when no path is given.
  git-checkout.txt: fix incorrect statement about HEAD and index

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

diff --cc Documentation/gitattributes.txt
Simple merge