diff --git a/lib/bundler/source/git.rb b/lib/bundler/source/git.rb
index f7ad6057b46b79..4a9f3731bd1f56 100644
--- a/lib/bundler/source/git.rb
+++ b/lib/bundler/source/git.rb
@@ -69,19 +69,7 @@ def eql?(other)
 
       def to_s
         begin
-          at = if local?
-            path
-          elsif user_ref = options["ref"]
-            if /\A[a-z0-9]{4,}\z/i.match?(ref)
-              shortref_for_display(user_ref)
-            else
-              user_ref
-            end
-          elsif ref
-            ref
-          else
-            current_branch
-          end
+          at = humanized_ref || current_branch
 
           rev = "at #{at}@#{shortref_for_display(revision)}"
         rescue GitError
@@ -91,6 +79,10 @@ def to_s
         uri_with_specifiers([rev, glob_for_display])
       end
 
+      def identifier
+        uri_with_specifiers([humanized_ref, cached_revision, glob_for_display])
+      end
+
       def uri_with_specifiers(specifiers)
         specifiers.compact!
 
@@ -256,6 +248,20 @@ def local?
 
       private
 
+      def humanized_ref
+        if local?
+          path
+        elsif user_ref = options["ref"]
+          if /\A[a-z0-9]{4,}\z/i.match?(ref)
+            shortref_for_display(user_ref)
+          else
+            user_ref
+          end
+        elsif ref
+          ref
+        end
+      end
+
       def serialize_gemspecs_in(destination)
         destination = destination.expand_path(Bundler.root) if destination.relative?
         Dir["#{destination}/#{@glob}"].each do |spec_path|
diff --git a/spec/bundler/install/gemfile/git_spec.rb b/spec/bundler/install/gemfile/git_spec.rb
index c96a78bc1cff22..910f96f4ab2aa7 100644
--- a/spec/bundler/install/gemfile/git_spec.rb
+++ b/spec/bundler/install/gemfile/git_spec.rb
@@ -30,6 +30,13 @@
       expect(Dir["#{default_bundle_path}/cache/bundler/git/foo-1.0-*"]).to have_attributes :size => 1
     end
 
+    it "does not write to cache on bundler/setup" do
+      cache_path = default_bundle_path.join("cache")
+      FileUtils.rm_rf(cache_path)
+      ruby "require 'bundler/setup'"
+      expect(cache_path).not_to exist
+    end
+
     it "caches the git repo globally and properly uses the cached repo on the next invocation" do
       simulate_new_machine
       bundle "config set global_gem_cache true"