Re: [PATCH v5 00/21] Sparse Index: Design, Format, Tests

>
> On 3/30/2021 4:11 PM, Junio C Hamano wrote:
> > "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> >
> >>      @@ repo-settings.c: void prepare_repo_settings(struct repository *r)
> >>       +       * Initialize this as off.
> >>       +       */
> >>       +      r->settings.sparse_index = 0;
> >>      -+      if (!repo_config_get_bool(r, "extensions.sparseindex", &value) && value)
> >>      ++      if (!repo_config_get_bool(r, "index.sparse", &value) && value)
> >>       +              r->settings.sparse_index = 1;
> >>        }
> >
> > It would be helpful to have a way for the repository owner to say
> > "Even if the version of Git may be capable of handling 'sdir'
> > extension, and my checkout uses sparse-cone settings, I do not want
> > to use it", and the other way around, i.e. "Even if my checkout
> > currently does not use sparse-cone settings, do use 'sdir'
> > extension".  But for that, .sparse_index member may need to be
> > tristate (i.e. forbidden, enable-if-needed, use-even-unneeded)?
>
> I believe as presented, index.sparse=false will prevent the sdir
> extension from being used. If index.sparse=true, then it will only
> be used if sparse-checkout is enabled in cone mode.
>
> I don't see the value in using the 'sdir' extension when not using
> sparse-checkout in cone mode (and hence there are no sparse directory
> entries in the index). What am I missing?
>
> > We have a similar setting in index.version; I believe we always
> > auto-demote 3 down to 2 when extended flags are not used, and
> > I think "always auto-demote" would be sufficient (iow,
> > "use-even-unneeded" may not be necessary, even though that might
> > help debugging).
>
> Yes, the same is happening here: we auto-demote to not use 'sdir'
> if it the other settings are not configured as well.
>
> There is the rare scenario where these things all occur:
>
> 1. index.sparse = true
> 2. core.sparseCheckout = true
> 3. core.sparseCheckoutCone = true
> 4. Every path in the index matches the cone-mode patterns.
>
> In this case, convert_to_sparse() is called and the istate->sparse
> bit is set, telling do_write_index() to add the 'sdir' extension.
>
> This seems like a rare occurrence. Is it still worth adding logic
> to avoid 'sdir' when these are all true?