line-range: teach -L^/RE/ to search from start of file
The -L/RE/ option of blame/log searches from the end of the previous -L
range, if any. Add new notation -L^/RE/ to override this behavior and
search from start of file.
The new ^/RE/ syntax is valid only as the <start> argument of
-L<start>,<end>. The <end> argument, as usual, is relative to <start>.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>