Include revision hash in Source::Git#to_sshow-git-rev

This effectively changes the output of commands that use Source::Git#to_s
(ie. `bundle install`). For example:

    Using rack 1.0.0 from git@github.com:rack/rack.git (at master@574b147)

Closes #3433.

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/bundler/source/git.rb b/lib/bundler/source/git.rb
index c18341d17e..3a75299ff8 100644
--- a/lib/bundler/source/git.rb
+++ b/lib/bundler/source/git.rb
@@ -65,7 +65,14 @@ module Bundler
         else
           ref
         end
-        "#{uri} (at #{at})"
+
+        rev = begin
+                "@#{shortref_for_display(revision)}"
+              rescue GitError
+                nil
+              end
+
+        "#{uri} (at #{at}#{rev})"
       end
 
       def name