Extract parse_align_position() from populate_value(), which, given a
string, would give us the alignment position. This is a preparatory
patch as to introduce prefixes for the %(align) atom and avoid
redundancy in the code.
Helped-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Karthik Nayak <Karthik.188@gmail.com> Reviewed-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>