pypa/pip — pull request #965 by anrs (2013-05-29 10:47:51+00:00)
Title: for git 1.8.3

in git 1.8.3 the default branch name is "detached from " 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.