Re: [PATCH 6/6] Retain caches of submodule refs

Michael Haggerty [off-list ref] writes:

So I think I need help from a submodule guru (Heiko?) who can tell me
what is done with submodule references and whether they might be
modified while a git process is executing in the main module.  If so,
then either this patch has to be withdrawn, or more work has to be put
in to make such code invalidate the submodule reference cache.

Sorry for the oversight, but I forgot that not all code necessarily uses
the refs.c API when dealing with references (a regrettable situation, BTW).

In the longer term, I would agree with you that we very much prefer all
the ref accesses to go through the refs API, and I also foresee that the
submodule support would need to become more aware of the status of refs in
checked out submodules. For example, a recursive "submodule update" may
want to inspect the refs in a submodule directory, compare them with the
commit bound in the superproject tree for the submodule path, and decide
to spawn a "fetch && checkout $branch" in there. The same process then may
want to run "status" at the superproject level to show the result, which
in turn would inspect the relationship between the commit bound in the
superproject tree and the commit at the HEAD of the submodule directory.

So let's not rip out the commit but instead give submodule machinery an
explicit way to say "We do not know the current status of the refs in this
submodule anymore".

Thanks.