create: add --ruby option

Library/Homebrew/dev-cmd/create.rb

@@ -31,6 +31,8 @@ module Homebrew
              description: "Create a basic template for a Perl build."
       switch "--python",
              description: "Create a basic template for a Python build."
+      switch "--ruby",
+             description: "Create a basic template for a Ruby build."
       switch "--rust",
              description: "Create a basic template for a Rust build."
       switch "--no-fetch",
@@ -86,6 +88,8 @@ module Homebrew
       :perl
     elsif args.python?
       :python
+    elsif args.ruby?
+      :ruby
     elsif args.rust?
       :rust
     end

Library/Homebrew/formula_creator.rb

@@ -112,6 +112,8 @@ module Homebrew
           uses_from_macos "perl"
         <% elsif  mode == :python %>
           depends_on "python"
+        <% elsif  mode == :ruby %>
+          uses_from_macos "ruby"
         <% elsif  mode == :rust %>
           depends_on "rust" => :build
         <% elsif  mode.nil? %>
@@ -166,6 +168,12 @@ module Homebrew
             bin.env_script_all_files(libexec/"bin", :PERL5LIB => ENV["PERL5LIB"])
         <% elsif  mode == :python %>
             virtualenv_install_with_resources
+        <% elsif  mode == :ruby %>
+            ENV["GEM_HOME"] = libexec
+            system "gem", "build", "\#{name}.gemspec"
+            system "gem", "install", "\#{name}-\#{version}.gem"
+            bin.install libexec/"bin/\#{name}"
+            bin.env_script_all_files(libexec/"bin", :GEM_HOME => ENV["GEM_HOME"])
         <% elsif  mode == :rust %>
             system "cargo", "install", "--locked", "--root", prefix, "--path", "."
         <% else  %>

docs/Manpage.md

@@ -813,6 +813,8 @@ a simple example. For the complete API, see:
   Create a basic template for a Perl build.
 * `--python`:
   Create a basic template for a Python build.
+* `--ruby`:
+  Create a basic template for a Ruby build.
 * `--rust`:
   Create a basic template for a Rust build.
 * `--no-fetch`:

manpages/brew.1

@@ -1044,6 +1044,10 @@ Create a basic template for a Perl build\.
 Create a basic template for a Python build\.
 .
 .TP
+\fB\-\-ruby\fR
+Create a basic template for a Ruby build\.
+.
+.TP
 \fB\-\-rust\fR
 Create a basic template for a Rust build\.
 .