formula_auditor: split audit_revision_and_version_scheme.

Separate this into two methods so we can have separate skips for each.

Library/Homebrew/formula_auditor.rb

@@ -797,7 +797,7 @@ module Homebrew
       end
     end
 
-    def audit_revision_and_version_scheme
+    def audit_revision
       new_formula_problem("New formulae should not define a revision.") if @new_formula && !formula.revision.zero?
 
       return unless @git
@@ -806,20 +806,10 @@ module Homebrew
       return if formula.stable.blank?
 
       current_version = formula.stable.version
-      current_version_scheme = formula.version_scheme
       current_revision = formula.revision
 
       previous_committed, newest_committed = committed_version_info
 
-      unless previous_committed[:version_scheme].nil?
-        if current_version_scheme < previous_committed[:version_scheme]
-          problem "version_scheme should not decrease (from #{previous_committed[:version_scheme]} " \
-                  "to #{current_version_scheme})"
-        elsif current_version_scheme > (previous_committed[:version_scheme] + 1)
-          problem "version_schemes should only increment by 1"
-        end
-      end
-
       if (previous_committed[:version] != newest_committed[:version] ||
          current_version != newest_committed[:version]) &&
          !current_revision.zero? &&
@@ -836,6 +826,26 @@ module Homebrew
       end
     end
 
+    def audit_version_scheme
+      return unless @git
+      return unless formula.tap # skip formula not from core or any taps
+      return unless formula.tap.git? # git log is required
+      return if formula.stable.blank?
+
+      current_version_scheme = formula.version_scheme
+
+      previous_committed, = committed_version_info
+
+      return if previous_committed[:version_scheme].nil?
+
+      if current_version_scheme < previous_committed[:version_scheme]
+        problem "version_scheme should not decrease (from #{previous_committed[:version_scheme]} " \
+                "to #{current_version_scheme})"
+      elsif current_version_scheme > (previous_committed[:version_scheme] + 1)
+        problem "version_schemes should only increment by 1"
+      end
+    end
+
     def audit_unconfirmed_checksum_change
       return unless @git
       return unless formula.tap # skip formula not from core or any taps

Library/Homebrew/test/dev-cmd/audit_spec.rb

@@ -961,10 +961,10 @@ module Homebrew
       end
     end
 
-    describe "#audit_revision_and_version_scheme" do
+    describe "#audit_revision" do
       subject do
         fa = described_class.new(Formulary.factory(formula_path), git: true)
-        fa.audit_revision_and_version_scheme
+        fa.audit_revision
         fa.problems.first&.fetch(:message)
       end
 
@@ -1001,7 +1001,7 @@ module Homebrew
             end
           RUBY
 
-          fa.audit_revision_and_version_scheme
+          fa.audit_revision
 
           expect(fa.new_formula_problems).to include(
             a_hash_including(message: a_string_matching(/should not define a revision/)),
@@ -1083,6 +1083,38 @@ module Homebrew
           it { is_expected.to be_nil }
         end
       end
+    end
+
+    describe "#audit_version_scheme" do
+      subject do
+        fa = described_class.new(Formulary.factory(formula_path), git: true)
+        fa.audit_version_scheme
+        fa.problems.first&.fetch(:message)
+      end
+
+      before do
+        origin_formula_path.dirname.mkpath
+        origin_formula_path.write <<~RUBY
+          class Foo#{foo_version} < Formula
+            url "https://brew.sh/foo-1.0.tar.gz"
+            sha256 "31cccfc6630528db1c8e3a06f6decf2a370060b982841cfab2b8677400a5092e"
+            revision 2
+            version_scheme 1
+          end
+        RUBY
+
+        origin_tap_path.mkpath
+        origin_tap_path.cd do
+          system "git", "init"
+          system "git", "add", "--all"
+          system "git", "commit", "-m", "init"
+        end
+
+        tap_path.mkpath
+        tap_path.cd do
+          system "git", "clone", origin_tap_path, "."
+        end
+      end
 
       describe "version_schemes" do
         describe "should not decrease with the same version" do