Re: [PATCH] fetch: document that pruning happens before fetching

From: Jeff King <peff@peff.net>
Date: Jun 14, 2016, 06:17 UTC
Message-ID: <20160614061752.GA11935@sigill.intra.peff.net>
In-Reply-To: <CA+P7+xpk6HqeJfUcAkpTbW_hO6dyjanXoqaaKqdTU363n=-Stw@mail.gmail.com>

On Mon, Jun 13, 2016 at 11:14:36PM -0700, Jacob Keller wrote:

Show 29 quoted lines

> On Mon, Jun 13, 2016 at 4:58 PM, Jeff King <peff@peff.net> wrote:
> > This was changed in 10a6cc8 (fetch --prune: Run prune before
> > fetching, 2014-01-02), but it seems that nobody in that
> > discussion realized we were advertising the "after"
> > explicitly.
> >
> > Signed-off-by: Jeff King <peff@peff.net>
> > ---
> > I include myself in that "nobody" of course. :)
> >
> >  Documentation/fetch-options.txt | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
> > index 036edfb..b05a834 100644
> > --- a/Documentation/fetch-options.txt
> > +++ b/Documentation/fetch-options.txt
> > @@ -52,7 +52,7 @@ ifndef::git-pull[]
> >
> >  -p::
> >  --prune::
> > -       After fetching, remove any remote-tracking references that no
> > +       Before fetching, remove any remote-tracking references that no
> >         longer exist on the remote.  Tags are not subject to pruning
> >         if they are fetched only because of the default tag
> >         auto-following or due to a --tags option.  However, if tags
> 
> What's the difference in behavior due to pruning before instead of
> after? Curious. It seems like pruning after would make more sense?

See 10a6cc8. :)

Basically, you have to prune first to make way for new incoming refs when there is a D/F conflict.

The downside is that there is a moment where objects may be unreferenced (e.g., if upstream moved "foo" to "bar", we delete "foo" and _then_ create "bar"). And due to the way refs are stored, we do not keep even a reflog for the deleted ref in the interim.

-Peff