pre-push.sample: Make the script executable

githooks(5) says that "[...]the .sample files are executable by default"
which was not true.

Signed-off-by: Wieland Hoffmann <themineo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t0070 "mktemp to unwritable directory" needs SANITY

Use the SANITY prerequisite when testing if a temp file can
be created in a read only directory.
Skip the test under CYGWIN, or skip it under Unix/Linux when
it is run as root.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>