Fix swap-deps to use correct Bundler syntax for Git tags (#38)

lib/demo_scripts/gem_swapper.rb

@@ -278,9 +278,17 @@ def swap_gem_to_github(content, gem_name, info)
         # Extract options after version (if any)
         options = rest.sub(/^\s*,\s*(['"])[^'"]*\1/, '') # Remove version if present
 
-        # Build replacement: gem 'name', github: 'user/repo', branch: 'branch-name' [, options...]
+        # Use tag: for tags, branch: for branches (default to :branch if not specified)
+        ref_type = info[:ref_type] || :branch
+        param_name = ref_type == :tag ? 'tag' : 'branch'
+
+        # Only omit ref when it's a branch (not tag) and the branch is 'main' or 'master'
+        # Tags must always be explicit, even if named 'main' or 'master'
+        should_omit_ref = ref_type == :branch && %w[main master].include?(info[:branch])
+
+        # Build replacement: gem 'name', github: 'user/repo', branch/tag: 'ref-name' [, options...]
         replacement = "#{indent}gem #{quote}#{gem_name}#{quote}, github: #{quote}#{info[:repo]}#{quote}"
-        replacement += ", branch: #{quote}#{info[:branch]}#{quote}" if info[:branch] != 'main'
+        replacement += ", #{param_name}: #{quote}#{info[:branch]}#{quote}" unless should_omit_ref
         replacement += options unless options.strip.empty?
         replacement
       end

spec/demo_scripts/gem_swapper_spec.rb

@@ -165,6 +165,46 @@
         expect(result).to eq("gem 'shakapacker', github: 'shakacode/shakapacker', branch: 'develop', require: false\n")
       end
     end
+
+    context 'with tag instead of branch' do
+      let(:gemfile_content) { "gem 'shakapacker', '~> 9.0.0'\n" }
+      let(:github_info) { { repo: 'shakacode/shakapacker', branch: 'v1.0.0', ref_type: :tag } }
+
+      it 'uses tag parameter instead of branch' do
+        result = swapper.send(:swap_gem_to_github, gemfile_content, 'shakapacker', github_info)
+        expect(result).to eq("gem 'shakapacker', github: 'shakacode/shakapacker', tag: 'v1.0.0'\n")
+      end
+    end
+
+    context 'with explicit branch ref_type' do
+      let(:gemfile_content) { "gem 'shakapacker', '~> 9.0.0'\n" }
+      let(:github_info) { { repo: 'shakacode/shakapacker', branch: 'develop', ref_type: :branch } }
+
+      it 'uses branch parameter' do
+        result = swapper.send(:swap_gem_to_github, gemfile_content, 'shakapacker', github_info)
+        expect(result).to eq("gem 'shakapacker', github: 'shakacode/shakapacker', branch: 'develop'\n")
+      end
+    end
+
+    context 'with tag named main' do
+      let(:gemfile_content) { "gem 'shakapacker', '~> 9.0.0'\n" }
+      let(:github_info) { { repo: 'shakacode/shakapacker', branch: 'main', ref_type: :tag } }
+
+      it 'includes tag parameter even though it is named main' do
+        result = swapper.send(:swap_gem_to_github, gemfile_content, 'shakapacker', github_info)
+        expect(result).to eq("gem 'shakapacker', github: 'shakacode/shakapacker', tag: 'main'\n")
+      end
+    end
+
+    context 'with master branch' do
+      let(:gemfile_content) { "gem 'shakapacker', '~> 9.0.0'\n" }
+      let(:github_info) { { repo: 'shakacode/shakapacker', branch: 'master', ref_type: :branch } }
+
+      it 'omits branch parameter for master (like main)' do
+        result = swapper.send(:swap_gem_to_github, gemfile_content, 'shakapacker', github_info)
+        expect(result).to eq("gem 'shakapacker', github: 'shakacode/shakapacker'\n")
+      end
+    end
   end
 
   describe '#swap_package_json' do