Re: [RFC PATCH] checkout: Force matching mtime between files

From: Junio C Hamano <gitster@pobox.com>
Date: Apr 25, 2018, 08:48 UTC
Message-ID: <xmqqin8f4qoq.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <robbat2-20180425T060717-325652820Z@orbis-terrarum.net>

"Robin H. Johnson" <robbat2@gentoo.org> writes:

Show 7 quoted lines

> In the thread from 6 years ago, you asked about tar's behavior for
> mtimes. 'tar xf' restores mtimes from the tar archive, so relative
> ordering after restore would be the same, and would only rebuild if the
> original source happened to be dirty.
>
> This behavior is already non-deterministic in Git, and would be improved
> by the patch.

But Git is not an archiver (tar), but is a source code control system, so I do not think we should spend any extra cycles to "improve" its behaviour wrt the relative ordering, at least for the default case. Only those who rely on having build artifact *and* source should pay the runtime (and preferrably also the maintainance) cost.

The best approach to do so is to have those people do the "touch" thing in their own post-checkout hook. People who use Git as the source control system won't have to pay runtime cost of doing the touch thing, and we do not have to maintain such a hook script. Only those who use the "feature" would.