Move head-only checks to cmd/install

Fixes Homebrew/homebrew#30084.
Closes Homebrew/homebrew#30203.

Library/Homebrew/cmd/install.rb

@@ -24,6 +24,21 @@ module Homebrew extend self
       end
     end unless ARGV.force?
 
+    ARGV.formulae.each do |f|
+      # Building head-only without --HEAD is an error
+      if not ARGV.build_head? and f.stable.nil?
+        raise CannotInstallFormulaError, <<-EOS.undent
+        #{f} is a head-only formula
+        Install with `brew install --HEAD #{f.name}`
+        EOS
+      end
+
+      # Building stable-only with --HEAD is an error
+      if ARGV.build_head? and f.head.nil?
+        raise CannotInstallFormulaError, "No head is defined for #{f.name}"
+      end
+    end
+
     perform_preinstall_checks
 
     begin

Library/Homebrew/formula_installer.rb

@@ -109,19 +109,6 @@ class FormulaInstaller
       raise FormulaAlreadyInstalledError, msg
     end
 
-    # Building head-only without --HEAD is an error
-    if not ARGV.build_head? and f.stable.nil?
-      raise CannotInstallFormulaError, <<-EOS.undent
-        #{f} is a head-only formula
-        Install with `brew install --HEAD #{f.name}
-      EOS
-    end
-
-    # Building stable-only with --HEAD is an error
-    if ARGV.build_head? and f.head.nil?
-      raise CannotInstallFormulaError, "No head is defined for #{f.name}"
-    end
-
     unless ignore_deps?
       unlinked_deps = f.recursive_dependencies.map(&:to_formula).select do |dep|
         dep.installed? and not dep.keg_only? and not dep.linked_keg.directory?