bundle-exec.ronn in bundler-1.16.0.pre.1

- old
+ new
@@ -61,9 +61,16 @@
   prevent gems from the system leaking into the environment
 * Override `Gem.bin_path` to use the gems in the bundle,
   making system executables work
 * Add all gems in the bundle into Gem.loaded_specs
 
+Finally, `bundle exec` also implicitly modifies `Gemfile.lock` if the lockfile
+and the Gemfile do not match. Bundler needs the Gemfile to determine things
+such as a gem's groups, `autorequire`, and platforms, etc., and that
+information isn't stored in the lockfile. The Gemfile and lockfile must be
+synced in order to `bundle exec` successfully, so `bundle exec`
+updates the lockfile beforehand.
+
 ### Loading
 
 By default, when attempting to `bundle exec` to a file with a ruby shebang,
 Bundler will `Kernel.load` that file instead of using `Kernel.exec`. For the
 vast majority of cases, this is a performance improvement. In a rare few cases,