Merge branch 'jc/alias-completion'

The command line completion script (in contrib/) can be told to complete aliases by including ": git <cmd> ;" in the alias to tell it that the alias should be completed similar to how "git <cmd>" is completed. The parsing code for the alias as been loosened to allow ';' without an extra space before it. * jc/alias-completion: completion: loosen and document the requirement around completing alias