Re: [PATCH 0/2] describe and diff: implement --no-optional-locks

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> .... What
> git-status does with --no-optional-locks is to update the index
> internally for its _own_ use (giving it the correct results), but not to
> lock nor write out the resulting index (to avoid conflicting with other
> running programs). So it's pessimal (losing the opportunity to share
> what it learned) but prevents lock contention.

Yup, that sounds somewhat sensible.  I also have to wonder, other
than commands that are clearly about changing the repository state
like "add", the inspection commands like diff and status should
always opportunistically write the index back, without even being
asked?

> ... Either it must:
>
>   - accept that diff-files might return stat-dirty results (yuck)
>
>   - use its own index that is separate from the regular .git/index file.
>     But that may be overly slow, since the index "update" would rewrite
>     the whole thing from scratch. Of course all of our index writes are
>     from scratch, but you'd pay the price even when there is nothing to
>     update.
>
>   - use a command which operates all in a single process, with an
>     in-memory index that is updated but not written out (e.g., "git
>     --no-optional-locks status").