Re: [PATCH 3/3] commit-graph: error out on invalid commit oids in 'write --stdin-commits'

From: Taylor Blau <me@ttaylorr.com>
Date: Apr 3, 2020, 19:57 UTC
Message-ID: <20200403195736.GB58262@syl.local>
In-Reply-To: <xmqqd08oz70o.fsf@gitster.c.googlers.com>

On Fri, Apr 03, 2020 at 12:47:03PM -0700, Junio C Hamano wrote:

Show 35 quoted lines

> Taylor Blau <me@ttaylorr.com> writes:
>
> > On Fri, Apr 03, 2020 at 02:30:57PM -0400, Jeff King wrote:
> >> On Mon, Aug 05, 2019 at 10:02:40AM +0200, SZEDER Gábor wrote:
> >>
> >> > Check that all input records are indeed valid commit object ids and
> >> > return with error otherwise, the same way '--stdin-packs' handles
> >> > invalid input; see e103f7276f (commit-graph: return with errors during
> >> > write, 2019-06-12).
> >>
> >> Can you explain more why the old behavior is a problem? For reasons (see
> >> below), we want to do something like:
> >>
> >>   git for-each-ref --format='%(objectname)' |
> >>   git commit-graph write --stdin-commits
> >> ...
> >>  - you're generating an incremental graph update. You know somehow that
> >>    a few refs were updated, and you want to feed those tips to generate
> >>    the incremental, but not the rest of the refs (not because it would
> >>    be wrong to do so, but in the name of keeping it O(size of change)
> >>    and not O(number of refs in the repo).
> >> ...
> >> Normally I'm in favor of more error checking instead of less, but in
> >> this case it feels like it's putting scripted use at a disadvantage
> >> versus the internal code (e.g., the auto-write for git-fetch uses the
> >> "--reachable" semantics for its internal invocation).
>
> I think the "incremental from the tip of refs" is a valid and useful
> use case.  I am not sure if the rationale given in the original to
> compare the (stricter) check done here and what e103f7276f did
> (which does not seem to get any input, valid or invalid, from the
> end users) was a meaningful comparison, and regardless of Gábor's
> answer to Peff's question, I think we should have an easy way to let
> the machinery itself filter non-commit, so "--[no-]check-oids" that
> optionally turns the stricter checking off would be an easy way out.

Thanks. I think that this is probably my preference, too. I'll send this as a patch to the list shortly...

> I do not have a strong opinion on which way the default should be
> (at least not yet), but given that this was already in two major
> releases ago, I'd assume that stricter-by-default-with-escape-hatch
> would be the way to go (at least for now).

Yeah. I think the nice thing about those patches is that we don't have to decide that right away.

Show 13 quoted lines

> > For what it's worth, (and in case it wasn't obvious) this came about
> > because we feed '--stdin-commits' at GitHub, and observed exactly this
> > error case. I wasn't sure what approach would be more palatable, so I
> > prepared both in my fork at https://github.com/ttaylorr/git:
> >
> >   - Branch 'tb/commit-graph-dont-check-oids' drops this checking
> >     entirely.
> >
> >   - Branch 'tb/commit-graph-check-oids-option' adds a
> >     '--[no-]check-oids', in case that this is generally desirable
> >     behavior, by offering an opt-out of this OID checking.
>
> Thanks.

Likewise :).

Thanks, Taylor