git: Use -z for null separated parsing

[jerry-skydio]

Some git commands using paths will escape unicode characters, which
we then don't handle properly.

Fix this by passing -z so git doesn't escape these, and splitting on nulls.

Add a test

[jerry-skydio]

Reviews in this chain:
└#267 amend: Fix last-touched functionality
　└#276 amend: Fix last-touched when deleting files
　　└#278 git: Use -z for null separated parsing

[jerry-skydio]

#	head	base	diff	date	summary
0	23876b43	e70a81fe	diff	Jul 23 16:14 PM	3 files changed, 37 insertions(+), 8 deletions(-)
1	9c4b3f18	f5bb77dd	rebase	Jul 27 13:47 PM	0 files changed