Adapt tutorial to cygwin and add test case

Lacking reliable symlinks, the instructions in the tutorial did not work
in a cygwin setup. Also, a few outputs were not correct.

This patch fixes these, and adds a test case which follows the
instructions of the tutorial (except git-clone, -fetch and -push, which I
have not done yet).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>