t6050: check pushing something based on a replaced commit

t6050: check pushing something based on a replaced commit

When using something like:

$ git push $there 04a8c^2:master

we need to parse 04a8c to find its second parent and then start
discussing what object to send with the other end.  "04a8c^2" is a direct
user input and should mean the same commit as git show "04a8c^2" would
give the user, so it obviously needs to obey the replace rules (making
04a8c parsed), but the object transfer should not look at replace at all.

This patch adds some tests to check that the above is working well.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>