Disallow head do blocks with only url and branch

- Since `head` must now specify a url and branch, the `head do` block
  with only these stanzas can be condensed to the single-line
  `head "url", branch: "branch"` format.

Author: issyl0

Library/Homebrew/rubocops/components_redundancy.rb

@@ -13,7 +13,7 @@ module FormulaAudit
       # - `bottle :unneeded`/`:disable` and `bottle do` should not be simultaneously present
       # - `stable do` should not be present without a `head` spec
       # - `stable do` should not be present with only `url|checksum|mirror|version`
-      # - `head do` should not be present with only `url`
+      # - `head do` should not be present with only `url|branch`
       class ComponentsRedundancy < FormulaCop
         HEAD_MSG = "`head` and `head do` should not be simultaneously present"
         BOTTLE_MSG = "`bottle :modifier` and `bottle do` should not be simultaneously present"
@@ -54,8 +54,9 @@ def audit_formula(formula_nodes)
           head_block = find_block(body_node, :head)
           if head_block && !head_block.body.nil?
             child_nodes = head_block.body.begin_type? ? head_block.body.child_nodes : [head_block.body]
-            if child_nodes.all? { |n| n.send_type? && n.method_name == :url }
-              problem "`head do` should not be present with only `url`"
+            shorthand_head_methods = [:url, :branch]
+            if child_nodes.all? { |n| n.send_type? && shorthand_head_methods.include?(n.method_name) }
+              problem "`head do` should not be present with only #{shorthand_head_methods.join("/")}"
             end
           end
 

Library/Homebrew/test/rubocops/components_redundancy_spec.rb

@@ -82,13 +82,38 @@ class Foo < Formula
           end
 
           head do
-          ^^^^^^^ FormulaAudit/ComponentsRedundancy: `head do` should not be present with only `url`
+          ^^^^^^^ FormulaAudit/ComponentsRedundancy: `head do` should not be present with only url/branch
             url "https://brew.sh/foo.git"
           end
         end
       RUBY
     end
 
+    it "reports an offense if `head do` is present with only `url` and `branch`" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+
+          head do
+          ^^^^^^^ FormulaAudit/ComponentsRedundancy: `head do` should not be present with only url/branch
+            url "https://brew.sh/foo.git"
+            branch "develop"
+          end
+        end
+      RUBY
+
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+
+          head do
+          ^^^^^^^ FormulaAudit/ComponentsRedundancy: `head do` should not be present with only url/branch
+            url "https://brew.sh/foo.git", branch: "develop"
+          end
+        end
+      RUBY
+    end
+
     it "reports no offenses if `stable do` is present with `url` and `depends_on`" do
       expect_no_offenses(<<~RUBY)
         class Foo < Formula