Merge pull request #9294 from ianks/ianks/git-proxy-revision-fix

Ensure revision is always re-resolved in `git_proxy.rb`

(cherry picked from commit d3512d0)

Author: hsbt

bundler/lib/bundler/source/git/git_proxy.rb

@@ -137,7 +137,7 @@ def copy_to(destination, submodules = false)
             git "fetch", "--force", "--quiet", *extra_fetch_args(ref), dir: destination
           end
 
-          git "reset", "--hard", @revision, dir: destination
+          git "reset", "--hard", revision, dir: destination
 
           if submodules
             git_retry "submodule", "update", "--init", "--recursive", dir: destination