definition.rb in bundler-1.10.0.pre.1

- old
+ new

@@ -247,9 +247,19 @@
       if Bundler.settings[:frozen]
         Bundler.ui.error "Cannot write a changed lockfile while frozen."
         return
       end
 
+      if @locked_bundler_version
+        locked_major = @locked_bundler_version.segments.first
+        current_major = Gem::Version.create(Bundler::VERSION).segments.first
+
+        if locked_major < current_major
+          Bundler.ui.warn "Warning: the lockfile is being updated to Bundler #{Bundler::VERSION.split('.').first}, " \
+                          "after which you will be unable to return to Bundler #{@locked_bundler_version.segments.first}."
+        end
+      end
+
       File.open(file, 'wb'){|f| f.puts(contents) }
     rescue Errno::EACCES
       raise Bundler::InstallError,
         "There was an error while trying to write to Gemfile.lock. It is likely that \n" \
         "you need to allow write permissions for the file at path: \n" \