feat: Add Gemfile.lock to google-cloud-spanner (#238)

Add Gemfile.lock to the handwritten library to ensure consistent dependency versions in development and CI. Update CONTRIBUTING.md to remove the incorrect root-level bundle install instruction and add a note about managing Gemfile.lock. Fix NameError in doctest_helper.rb by explicitly requiring 'ostruct'. Update gemspec to reject Gemfile.lock from package files.

Addresses b/509981628

Co-authored-by: Torrey Payne <torreypayne@google.com>

Author: torreypayne

CONTRIBUTING.md

@@ -35,19 +35,15 @@ there is a small amount of setup:
    $ gem install bundler
    ```
 
-3. Install the top-level project dependencies.
-
-   ```sh
-   $ bundle install
-   ```
-
-4. Install the Spanner dependencies.
+3. Install the Spanner dependencies.
 
    ```sh
    $ cd google-cloud-spanner/
    $ bundle install
    ```
 
+   Note: We commit `Gemfile.lock` to ensure consistent dependency versions in development and CI. If you update dependencies in `Gemfile` or `google-cloud-spanner.gemspec`, make sure to run `bundle update` and commit the updated `Gemfile.lock`.
+
 ## Console
 
 In order to run code interactively, you can automatically load

google-cloud-spanner/.gitignore

@@ -1,4 +1,3 @@
-Gemfile.lock
 coverage/*
 doc/*
 pkg/*

google-cloud-spanner/CONTRIBUTING.md

@@ -35,19 +35,15 @@ there is a small amount of setup:
    $ gem install bundler
    ```
 
-3. Install the top-level project dependencies.
-
-   ```sh
-   $ bundle install
-   ```
-
-4. Install the Spanner dependencies.
+3. Install the Spanner dependencies.
 
    ```sh
    $ cd google-cloud-spanner/
    $ bundle install
    ```
 
+   Note: We commit `Gemfile.lock` to ensure consistent dependency versions in development and CI. If you update dependencies in `Gemfile` or `google-cloud-spanner.gemspec`, make sure to run `bundle update` and commit the updated `Gemfile.lock`.
+
 ## Console
 
 In order to run code interactively, you can automatically load