Change default branch for new Rails projects and plugins to main

This commit changes the default branch of new Rails projects
and plugins from master to main.

railties/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Change default branch for new Rails projects and plugins to `main`
+
+    *Prateek Choudhary*
+    
 *   Add benchmark method that can be called from anywhere.
 
     This method is used as a quick way to measure & log the speed of some code.

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -73,6 +73,9 @@ module Rails
     def version_control
       if !options[:skip_git] && !options[:pretend]
         run "git init", capture: options[:quiet], abort_on_failure: false
+        if user_default_branch.strip.empty?
+          `git symbolic-ref HEAD refs/heads/main`
+        end
       end
     end
 
@@ -265,6 +268,11 @@ module Rails
     def config_target_version
       defined?(@config_target_version) ? @config_target_version : Rails::VERSION::STRING.to_f
     end
+
+    private
+      def user_default_branch
+        @user_default_branch ||= `git config init.defaultbranch`
+      end
   end
 
   module Generators

railties/lib/rails/generators/rails/plugin/plugin_generator.rb

@@ -65,6 +65,9 @@ module Rails
     def version_control
       if !options[:skip_git] && !options[:pretend]
         run "git init", capture: options[:quiet], abort_on_failure: false
+        if user_default_branch.strip.empty?
+          `git symbolic-ref HEAD refs/heads/main`
+        end
       end
     end
 
@@ -178,6 +181,11 @@ task default: :test
         append_file gemfile_in_app_path, entry
       end
     end
+
+    private
+      def user_default_branch
+        @user_default_branch ||= `git config init.defaultbranch`
+      end
   end
 
   module Generators

railties/test/generators/app_generator_test.rb

@@ -1072,6 +1072,35 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_directory ".git"
   end
 
+  def test_default_branch_main_without_user_default
+    current_default_branch = `git config --global init.defaultBranch`
+    `git config --global --unset init.defaultBranch`
+
+    run_generator [destination_root]
+    assert_file ".git/HEAD", /main/
+  ensure
+    if !current_default_branch.strip.empty?
+      `git config --global init.defaultBranch #{current_default_branch}`
+    end
+  end
+
+  def test_version_control_initializes_git_repo_with_user_default_branch
+    git_version = `git --version`[/\d+.\d+.\d+/]
+    return if Gem::Version.new(git_version) < Gem::Version.new("2.28.0")
+
+    current_default_branch = `git config --global init.defaultBranch`
+    `git config --global init.defaultBranch master`
+
+    run_generator [destination_root]
+    assert_file ".git/HEAD", /master/
+  ensure
+    if current_default_branch && current_default_branch.strip.empty?
+      `git config --global --unset init.defaultBranch`
+    elsif current_default_branch
+      `git config --global init.defaultBranch #{current_default_branch}`
+    end
+  end
+
   def test_create_keeps
     run_generator
     folders_with_keep = %w(

railties/test/generators/plugin_generator_test.rb

@@ -91,6 +91,35 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_directory ".git"
   end
 
+  def test_initializes_git_repo_with_main_branch_without_user_default
+    current_default_branch = `git config --global init.defaultBranch`
+    `git config --global --unset init.defaultBranch`
+
+    run_generator
+    assert_file ".git/HEAD", /main/
+  ensure
+    if !current_default_branch.strip.empty?
+      `git config --global init.defaultBranch #{current_default_branch}`
+    end
+  end
+
+  def test_version_control_initializes_git_repo_with_user_default_branch
+    git_version = `git --version`[/\d+.\d+.\d+/]
+    return if Gem::Version.new(git_version) < Gem::Version.new("2.28.0")
+
+    current_default_branch = `git config --global init.defaultBranch`
+    `git config --global init.defaultBranch master`
+
+    run_generator
+    assert_file ".git/HEAD", /master/
+  ensure
+    if current_default_branch && current_default_branch.strip.empty?
+      `git config --global --unset init.defaultBranch`
+    elsif current_default_branch
+      `git config --global init.defaultBranch #{current_default_branch}`
+    end
+  end
+
   def test_generating_in_full_mode_with_almost_of_all_skip_options
     run_generator [destination_root, "--full", "-M", "-O", "-C", "-S", "-T", "--skip-active-storage"]
     assert_file "bin/rails" do |content|