Handle when delim isn't found but limit provided

A separator string could be provided that was not found in the stream.
In that scenario, we were ignoring the limit argument. This change
respects the limit argument even when the separator isn't found.

Author: jstuckey

lib/net/sftp/operations/file.rb

@@ -106,6 +106,10 @@ def gets(sep_or_limit=$/, limit=Float::INFINITY)
           @pos += offset
           line, @buffer = @buffer[0,offset], @buffer[offset..-1]
           return line
+        elsif lim < @buffer.length
+          @pos += lim
+          line, @buffer = @buffer[0,lim], @buffer[lim..-1]
+          return line
         elsif !fill
           return nil if @buffer.empty?
           @pos += @buffer.length

test/test_file.rb

@@ -106,6 +106,11 @@ def test_gets_with_delimiter_and_limit_should_read_to_limit_if_less_than_delimit
     assert_equal "hello", @file.gets("w", 5)
   end
 
+  def test_gets_when_no_such_delimiter_exists_in_stream_but_limit_provided_should_read_to_limit
+    @sftp.expects(:read!).returns("hello world\ngoodbye world\n\nfarewell!\n")
+    assert_equal "hello w", @file.gets("z", 7)
+  end
+
   def test_gets_at_EOF_should_return_nil
     @sftp.expects(:read!).returns(nil)
     assert_nil @file.gets