gistfile1.pp

$cwd='C:/Program Files (x86)/Puppet Labs/Puppet Enterprise/puppet/lib/puppet/type/file'
$patch='source.rb.patch'
$patchbin='C:\Tools\gnuwin32\bin\patch.exe'

  exec {"apply patch for ${title}":
    command => "${patchbin} -p0 < ${patch}",
    cwd     => $cwd,
    onlyif  => "${patchbin} -p0 -N --dry-run --silent < ${patch}",
  }

# I get this

debug: Exec[apply patch for source.rb.patch](provider=windows): Executing check 'C:\Tools\gnuwin32\bin\patch.exe -p0 -N
--dry-run --silent < source.rb.patch'
debug: Executing 'C:\Tools\gnuwin32\bin\patch.exe -p0 -N --dry-run --silent < source.rb.patch'
debug: /Stage[main]/Puppet::Agent::Windows/Iselib::Patch[source.rb.patch]/Exec[apply patch for source.rb.patch]/onlyif:
C:\Tools\gnuwin32\bin\patch.exe: **** File < is not a regular file -- can't patch

may need to do something like:

cmd.exe /c "C:\Tools\gnuwin32\bin\patch.exe -p0 -N --dry-run --silent < source.rb.patch"