Re: index-pack outside of repository?

[Jeff King <peff@peff.net>]

On Thu, Dec 15, 2016 at 04:13:38PM -0800, Junio C Hamano wrote:

> > So I think complaining to the user is the right thing to do here. I
> > started to write a patch to have index-pack notice when it needs a repo
> > and doesn't have one, but the logic is actually a bit unclear.  Do we
> > need to complain early _just_ when --stdin is specified, or does that
> > miss somes cases?  Likewise, are there cases where --stdin can operate
> > without a repo? I couldn't think of any.
> 
> I think there are two and only two major modes; --stdin wants to put
> the result in the repository it is working on, while the other mode
> takes a filename to deposit the result in, so the latter does not
> technically need a repository.

OK. That's easy to check for, then.  Reverse-engineering that logic from
the actual calls in index-pack.c:final() is complicated.  But certainly
basing it on --stdin is what I would have expected.

> > That strategy _might_ be a problem for some programs, which would want
> > to notice the issue early before doing work. But it seems like a
> > reasonable outcome for index-pack. Thoughts?
> 
> That is, once we know which codepaths should require a repository, I
> think it is reasonable to add a check that is done earlier than the
> place where we currently try to see where we have one (which could
> be deep in the callchain).  But we are all human and can miss things,
> so the BUG() thing is probably fine.  We are cooking it exactly because
> we would want to find such corner cases we missed, no?

Right, that was my original intent in adding the BUG(): to catch
unhandled cases, and then do the appropriate thing earlier. I was just
questioning whether the appropriate thing in some cases might be dying
at the BUG(), just with a more friendly message. That has the benefit of
being very easy to implement, and never wrong (e.g., forbidding a case
that actually _doesn't_ need to look at the repo).

But if this case really is just "if (from_stdin)" that's quite easy,
too.

-Peff