When copying a mcz to a gitfiletree repo, keep the timestamp

[ThierryGoubier]

As it says: ask git commit to reuse the timestamp present in the mcz.

[ThierryGoubier]

Results are weird. Date is changed in the log, but commit ordering isn't... so you can get older package version before a newer one.

[ThierryGoubier]

Ok. Just only activate setting the date when you also set the author name and email... this means you are copying a old mcz and you want to preserve in git that history. In 595acc5