The earlier test stripped away expected number of 'z' but the output
would have been very hard to read once somebody broke the common tail
optimization. Instead, count the number of 'z' and show it, to help
diagnosing the problem better in the future.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We need to be extra careful recovering the removed common section, so
that we do not break context nor the changed incomplete line (i.e. the
last line that does not end with LF).
Signed-off-by: Junio C Hamano <gitster@pobox.com>