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

[Duy Nguyen <pclouds@gmail.com>]

On Thu, Apr 26, 2018 at 4:46 PM, Michał Górny <mgorny@gentoo.org> wrote:
> For the record, we're using this with ebuilds and respective cache files
> (which are expensive to generate).  We are using separate repository
> which combines sources and cache files to keep the development
> repository clean.  I have researched different solutions for this but
> git turned out the best option for incremental updates for us.
>
> Tarballs are out of question, unless you expect users to fetch >100 MiB
> every time, and they are also expensive to update.  Deltas of tarballs
> are just slow and require storing a lot of extra data.  Rsync is not
> very efficient at frequent updates, and has significant overhead
> on every run.  With all its disadvantages, git is still something that
> lets our users fetch updates frequently with minimal network overhead.

I assume you're talking about the metadata directory in gentoo-x86
repo. This specific case could be solved by renaming metadata to
_metadata or something to put it on the top. "git checkout" always
updates files in strcmp(path) order. This guarantees time(_metadata)
<= time(ebuild) for all ebuilds without any extra touching (either in
git or in a post-checkout hook)

The behavior has been this way since forever and as far as I can tell
very unlikely to change at least for branch switching (major changes
involved around the index). It's a bit easier to accidentally change
how "git checkout -- path" works though. I don't know if we could just
make this checkout order a promise and guarantee not to break it
though. For it it does not sound like it adds extra maintenance
burden.
-- 
Duy