Add some specifics on gems (and maybe pips)

docs/Formula-Cookbook.md

@@ -60,6 +60,8 @@ Run `brew create` with a URL to the source tarball:
 brew create https://example.com/foo-0.1.tar.gz
 ```
 
+Passing in `--ruby` or `--python` will populate various defaults commonly useful for projects written in those languages.
+
 This creates `$(brew --repository)/Library/Taps/homebrew/homebrew-core/Formula/f/foo.rb` and opens it in your `EDITOR`. If run without any options to customize the output for specific build systems (check `brew create --help` to see which are available) it'll look something like:
 
 ```ruby
@@ -251,7 +253,36 @@ uses_from_macos "curl", since: :monterey
 
 Homebrew doesn’t package already-packaged language-specific libraries. These should be installed directly from `gem`/`cpan`/`pip` etc.
 
-If you're installing an application then use [`resource`](https://rubydoc.brew.sh/Formula#resource-class_method)s for all language-specific dependencies:
+### Ruby Gem Dependencies
+
+The preferred mechanism for installing gem dependencies is to use `bundler` with the upstream's `Gemfile.lock`. This requires the upstream checks in their `Gemfile.lock`, so if they don't, it's a good idea to file an issue and ask them to do so. Assuming they have one, this is as simple as:
+
+```ruby
+ENV["GEM_HOME"] = libexec
+system "bundle", "install", "--without", "development"
+```
+
+From there, you can build and install the project itself:
+
+```ruby
+system "gem", "build", "<project>.gemspec"
+system "gem", "install", "--ignore-dependencies", "<project>-#{version}.gem"
+```
+
+And install any bins, and munge their shebang lines, with:
+
+```ruby
+bin.install libexec/"bin/<bin>"
+bin.env_script_all_files(libexec/"bin", GEM_HOME: ENV["GEM_HOME"])
+```
+
+### Python dependencies
+
+For python we [`resource`](https://rubydoc.brew.sh/Formula#resource-class_method)s for dependencies and there's automation to generate these for you. Running `brew update-python-resources <formula>` will automatically add the necessary [`resource`](https://rubydoc.brew.sh/Formula#resource-class_method) stanzas for the dependencies of your Python application to the formula. Note that `brew update-python-resources` is run automatically by `brew create` if you pass the `--python` switch. If `brew update-python-resources` is unable to determine the correct `resource` stanzas, [homebrew-pypi-poet](https://github.com/tdsmith/homebrew-pypi-poet) is a good third-party alternative that may help.
+
+### All other cases
+
+If all else fails, you'll want to use [`resource`](https://rubydoc.brew.sh/Formula#resource-class_method)s for all other language-specific dependencies. This requires you to specify both a specific URL for a version and the sha256 checksum for security. Here's an example:
 
 ```ruby
 class Foo < Formula
@@ -268,8 +299,6 @@ end
 
 [`jrnl`](https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/j/jrnl.rb) is an example of a formula that does this well. The end result means the user doesn't have to use `pip` or Python and can just run `jrnl`.
 
-For Python formulae, running `brew update-python-resources <formula>` will automatically add the necessary [`resource`](https://rubydoc.brew.sh/Formula#resource-class_method) stanzas for the dependencies of your Python application to the formula. Note that `brew update-python-resources` is run automatically by `brew create` if you pass the `--python` switch. If `brew update-python-resources` is unable to determine the correct `resource` stanzas, [homebrew-pypi-poet](https://github.com/tdsmith/homebrew-pypi-poet) is a good third-party alternative that may help.
-
 ### Install the formula
 
 ```sh