Re: [RFC/PATCH] Disallow commands from within unpopulated submodules.

On Thu, Jan 19, 2017 at 11:30:23AM -0800, Stefan Beller wrote:

Now let's ask the same question for "git -C sub status ." (which is a
command that is only reading and not writing to the repository)

1) If the submodule is populated, the user clearly intended to know
   more about the submodules status
2) It is unclear if the user wanted to learn about the submodules state
   (So ideally: "The submodule 'sub' is not initialized. To init ...")
   or the status check should be applied to the superproject instead.

Avoid the confusion in 2) as well and just error out for now. Later on
we may want to add another flag to git.c to allow commands to be run
inside unpopulated submodules and each command reacts appropriately.

I like the general idea of catching commands in unpopulated submodules,
but I'm somewhat uncomfortable with putting an unconditional check into
git.c, for two reasons:

  1. Reading the index can be expensive. You would not want "git
     rev-parse" to incur this cost.

  2. How does this interact with commands which do interact with the
     index? Don't they expect to find the_index unpopulated?

     (I notice that it's effectively tied to RUN_SETUP, which is good.
      But that also means that many commands, like "diff", won't get the
      benefit. Not to mention non-builtins).

I'd rather see it in the commands themselves. Especially given the
"ideal" in your status example, which requires command-specific
knowledge.

-Peff