The emit_hunk_header() function is responsible for assembling a
hunk header and calling emit_line() to send the hunk header
to the output file. Its only caller fn_out_consume() needs
to prepare for a case where the function emits an incomplete
line and add the terminating LF.
Instead make sure emit_hunk_header() to always send a
completed line to emit_line().
Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>