Let commands decide what mode the installer should use

Library/Homebrew/cmd/install.rb

@@ -104,6 +104,8 @@ module Homebrew extend self
 
   def install_formula f
     fi = FormulaInstaller.new(f)
+    fi.ignore_deps = ARGV.ignore_deps? || ARGV.interactive?
+    fi.only_deps = ARGV.only_deps?
     fi.prelude
     fi.install
     fi.caveats

Library/Homebrew/cmd/upgrade.rb

@@ -59,6 +59,7 @@ module Homebrew extend self
     installer = FormulaInstaller.new(f)
     installer.options |= Tab.for_formula(f).used_options
     installer.show_header = false
+    installer.ignore_deps = false
     installer.prelude
 
     oh1 "Upgrading #{f.name}"

Library/Homebrew/formula_installer.rb

@@ -22,8 +22,8 @@ class FormulaInstaller
   def initialize ff
     @f = ff
     @show_header = false
-    @ignore_deps = ARGV.ignore_deps? || ARGV.interactive?
-    @only_deps = ARGV.only_deps?
+    @ignore_deps = false
+    @only_deps = false
     @options = Options.new
 
     @@attempted ||= Set.new
@@ -311,7 +311,6 @@ class FormulaInstaller
     fi.options |= dep.options
     fi.options |= inherited_options
     fi.ignore_deps = true
-    fi.only_deps = false
     fi.show_header = false
     fi.prelude
     oh1 "Installing #{f} dependency: #{Tty.green}#{dep.name}#{Tty.reset}"