RFR: vcs: support setting dates for tags

[Robin Westberg]

On Mon, 24 Aug 2020 13:39:11 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that allows setting the date for tag objects.
> 
> Testing:
> - [x] `make test` passes on Linux x64
> - [x] Added a new unit test
> 
> Thanks,
> Erik

Looks good!

-------------

Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/735