Subject: Re: Nesting a submodule inside of another...

From: Jens Lehmann <[email-masked]>
Date: Tue, 12 Jul 2011 21:23:13 +0200

Am 12.07.2011 14:01, schrieb John Szakmeister:
> I've got a project where we have several frameworks involved, and
> external modules we want to pull into the framework tree.  We'd like
> to make use of submodules and have something like this:
>     top-level/            <-- .gitmodules lives here
>         src/
>         framework1/   <-- a submodule
>             module/     <-- another submodule
>         framework2/   <-- a submodule
>             module2/    <-- another submodule
> 
> Currently, git fails trying to do this.  It's not happy about
> .gitmodules living at the top-level and nesting a submodule inside of
> another[1].  Is there a technical reason that this is not allowed?

Submodules are repositories of their own, so their work tree is outside
the superproject's work tree. You're attempting to have a submodule of
the superproject inside another submodule of the superproject, but this
won't work because it does not live in the superproject's work tree (as
that doesn't include submodules and their subdirectories).

To have nested submodules you must add "module" as a submodule of
"framework1" and "module2" as a submodule of "framework2". Then git
will handle them just fine (assuming you use the --recursive option for
"git submodule update" and friends). Of course that means that if you
want to record a new commit of a sub-submodule in the superpoject, you'll
have to commit that in it's parent submodule first and then can record
that commit in the superproject. (But if "framework1" wouldn't depend on
a specific version of "module", there would be no reason to put it inside
it in the first place, right?)

> Limiting the traversal up the tree, etc.?  I've worked around the lack
> of support to do this for now, but it would be really nice if we could
> do such a thing.

I can't think of a sane way to make that work.

> [1]  I may generate a patch for the error message, as the current
> implementation obscures the real error message.  When I try this, git
> says:
>     The following path is ignored by one of your .gitignore files:
>     framework1/module
>     Use -f if you really want to add it.
> 
>     After some careful debugging, I found out the real error message
> was about this sort of nesting being disallowed.

But at least since 1.6.2 git should issue a meaningful error message.
With current master I get:

$ git add sub/file
fatal: Path 'sub/file' is in submodule 'sub'

What version are you using?