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:
└#284 git: Use -z for null separated parsing

[jerry-skydio]

#	head	base	diff	date	summary
0	cb5d235a	fa73cdf5	diff	Jul 27 13:52 PM	3 files changed, 37 insertions(+), 8 deletions(-)
1	4d94381c	258238bd	rebase	Jul 27 13:54 PM	0 files changed
2	7ac3bf03	792fbe9f	diff	Jul 27 13:56 PM	0 files changed