Re: [PATCH 2/2] sparse-index: update index read to consider index.sparse config

Derrick Stolee [off-list ref] writes:

I think you are slightly mistaken here: If index.sparse=true, then a
full index will be converted to one on write, but not immediately upon
read. This means that subsequent commands will read a sparse index, and
they will either benefit from that or not depending on whether they are
integrated with the sparse index or not.

The new behavior here is that if index.sparse=false, then we convert
a sparse index to a full one upon read, avoiding any chance that a
Git command is operating on a sparse index in-memory.

And if index.sparse=true, then we convert a full on-disk index to a
sparse one in-core upon reading, right?  My comment was solely on
that side of the picture, not on the "index.sparse is set to false
so we automatically expand" case.

The simplest summary I can say is here:

* If index.sparse=false, then a sparse index will be converted to
  full upon read.

* If index.sparse=true, then a full index will be converted to sparse
  on write.

Oh, I see, so yes I was very much misunderstanding what you guys are
trying to do.  I somehow thought that sparse-to-full and
full-to-sparse conversions (1) already happen on the write codepath,
and (2) this patch makes them both happen also on the read codepath.

IOW:

    * If index.sparse=false, a sparse index will be written as full,
      and if it is true, a non-sparse index will be written as
      sparse, even before these patches.

    * In addition, with these patches, if index.sparse=false, a
      sparse index will be expaned to full upon reading, and if it
      is true, a non-sparse index will be shrunk to sparse upon
      reading

was what I was expecting.

What your summary above is saying is very much different.