Find git version in spec helper with git_proxy
Find git version in spec helper with git_proxy

This is minor, but duplicated code that also can be found in
`lib/bundler/source/git/git_proxy.rb`, so lets use that so we are
finding the git version in the same manner.  Bundler is fully loaded in
the spec helper anyway, so this is already available to be used.

mvz/bundler,dilumnavanjana/bundler,bundler/bundler,bundler/bundler,mvz/bundler,dilumnavanjana/bundler