Don't use Kernel.system much

It just seems to behave strangely with SIGINT. Eg. SIGINT causes tar to exit, but the SIGINT is ignored by our process. This is not the case when used with curl.

Library/Homebrew/formula_installer.rb

@@ -60,7 +60,7 @@ class FormulaInstaller
           exit! 1
         end
       end
-      ignore_interrupts do
+      ignore_interrupts do # because child proc will get it and marshall it back
         write.close
         Process.wait
         data = read.read

Library/Homebrew/test/unittest.rb

@@ -30,6 +30,24 @@ MACOS_VERSION=10.6
 Dir.chdir HOMEBREW_PREFIX
 at_exit { HOMEBREW_PREFIX.parent.rmtree }
 
+# for some reason our utils.rb safe_system behaves completely differently 
+# during these tests. This is worrying for sure.
+def safe_system *args
+  Kernel.system *args
+end
+
+class ExecutionError <RuntimeError
+  attr :status
+
+  def initialize cmd, args=[], status=nil
+    super "Failure while executing: #{cmd} #{args*' '}"
+    @status = status
+  end
+end
+
+class BuildError <ExecutionError
+end
+
 require 'test/unit' # must be after at_exit
 require 'extend/ARGV' # needs to be after test/unit to avoid conflict with OptionsParser
 ARGV.extend(HomebrewArgvExtension)

Library/Homebrew/utils.rb

@@ -69,27 +69,29 @@ def pretty_duration s
 end
 
 def interactive_shell
-  pid=fork
-  if pid.nil?
+  fork do
     # TODO make the PS1 var change pls
     #brown="\[\033[0;33m\]"
     #reset="\[\033[0m\]"
     #ENV['PS1']="Homebrew-#{HOMEBREW_VERSION} #{brown}\W#{reset}\$ "
     exec ENV['SHELL']
   end
-  Process.wait pid
-  raise SystemExit, "Aborting due to non-zero exit status" if $? != 0
+  Process.wait
+  unless $?.success?
+    puts "Aborting due to non-zero exit status"
+    exit $?
+  end
 end
 
 # Kernel.system but with exceptions
 def safe_system cmd, *args
   puts "#{cmd} #{args*' '}" if ARGV.verbose?
-  exec_success = Kernel.system cmd, *args
-  # some tools, eg. tar seem to confuse ruby and it doesn't propogate the
-  # CTRL-C interrupt to us too, so execution continues, but the exit code is
-  # still 2 so we raise our own interrupt
-  raise Interrupt, cmd if $?.termsig == 2
-  raise ExecutionError.new(cmd, args, $?) unless exec_success
+  fork do
+    trap("EXIT") {} # no bt on exit from this short-lived fork
+    exit! 1 unless exec(cmd, *args)
+  end
+  Process.wait
+  raise ExecutionError.new(cmd, args, $?) unless $?.success?
 end
 
 def curl *args