give a better error message when a remote ref no longer exists

if we can't find the given ref after fetching, try clearing the cache
ourselves and trying again. if we still can't find it, we know that it
actually just doesn't exist, so tell the user that.

1 files changed, 32 insertions, 3 deletions

diff --git a/lib/bundler/source/git/git_proxy.rb b/lib/bundler/source/git/git_proxy.rb
index b8900888a9..3b52843f7e 100644
--- a/lib/bundler/source/git/git_proxy.rb
+++ b/lib/bundler/source/git/git_proxy.rb
@@ -27,6 +27,13 @@ module Bundler
         end
       end
 
+      class GitRevisionError < GitError
+        def initialize(ref, repo)
+          msg = "Revision #{ref} does not exist in the repository #{repo}. Maybe you misspelled it?"
+          super msg
+        end
+      end
+
       # The GitProxy is responsible to interact with git repositories.
       # All actions required by the Git source is encapsulated in this
       # object.
@@ -44,10 +51,22 @@ module Bundler
         end
 
         def revision
-          @revision ||= allowed_in_path do
-            msg = "Ref '#{ref}' was not found. Perhaps you mispelled it?"
-            git("rev-parse --verify #{ref}", true, msg).strip
+          return @revision if @revision
+
+          begin
+            @revision ||= find_local_revision
+          rescue GitCommandError
+            Bundler.ui.info "Error finding #{ref} in #{path}: clearing the cache and trying again"
+            remove_cache
+            checkout
+            begin
+              @revision ||= find_local_revision
+            rescue GitCommandError
+              raise GitRevisionError.new(ref, uri)
+            end
           end
+
+          @revision
         end
 
         def branch
@@ -143,6 +162,16 @@ module Bundler
           false
         end
 
+        def remove_cache
+          FileUtils.rm_rf(path)
+        end
+
+        def find_local_revision
+          allowed_in_path do
+            git("rev-parse --verify #{ref}", true).strip
+          end
+        end
+
         # Escape the URI for git commands
         def uri_escaped_with_configured_credentials
           remote = configured_uri_for(uri)