pypa/pip — pull request #966 by anrs (2013-05-29 11:12:40+00:00)
Title: bugfix for Git >=1.8.3

bugfix for git 1.8.3, in git 1.8.3 the default branch name is "detached from REVISION" when you `git checkout -q `

if doesn't skip it then `git rev-parse ...` will raise a error while invoking Git._get_revision_from_rev_parse method.