bug#46905: Add a note about ext4's dir_index to the manual

[Ludovic Courtès]

Hi,

Tobias Geerinckx-Rice <me@tobias.gr> skribis:

> I should note that later in the IRC convo I corrected my sloppy ‘full’
> to ‘hash collision’.  Unfortunately it just returns an already
> overloaded -ENOSPC to user space.

OK, but when do we get ENOSPC, then?

> Ludovic Courtès 写道：

[...]

>> I don’t think we can claim there’s a design flaw.  WDYT?
>
> Fine; implementation flaw, then?  Problem is, it's not like there are
> other implementations than the one we're stuck with, so it matters
> little what we call it.

My point is that we shouldn’t suggest that ext4 + dir_index is flawed
or unsuitable for Guix use, because we have strong evidence suggesting
otherwise.  :-)

Now, I agree that if there are bugs or limitations hit in some
situations, we should document (or fix) them.

WDYT?

Thanks,
Ludo’.