Error fetching submodule from submodule

Hi I think I may have found an error in the way git handles a submodule's submodule. Read further for the example (extracted from a real project).

* I have a main repository which has some submodules defined.
* One of the submodules is a common submodule which is also included
in one of the other submodules
* When running `git fetch --recurse-submodules` I get an error.

The error is "Could not access submodule 'common_submodule'"

``` $ git --version git version 2.21.0 ```

I created the following script to show (using Git-extras `git create` to simplify):

``` #!/usr/bin/env bash

if [ "$FORCE" = 'true' ]; then
  rm -rf submodule_experiment
fi

if [ -e submodule_experiment ]; then
  echo FATAL: folder submodule_experiment must not exist. Remove with FORCE=true
  exit 9
fi

mkdir submodule_experiment pushd submodule_experiment

git setup common_submodule pushd common_submodule echo 'common file' > common.txt git add common.txt git commit -m 'a file in the common submodule'

popd

git setup other_submodule pushd other_submodule git submodule add ../common_submodule git commit -m 'added submodule to other_submodule'

popd

git setup main_repos pushd main_repos git submodule add ../common_submodule git commit -m 'added submodule to main_repos'

git submodule add ../other_submodule git commit -m 'added other_submodule to main_repos'

# This line fails with error code 1 "Could not access submodule 'common_submodule'" git fetch --recurse-submodules

```

Question: Is this a bug in Git or am I declaring the common submodule in an incorrect way?

On Thu, Mar 07, 2019 at 12:07:21PM +0100, Jesper Rønn-Jensen wrote:

First off, thank you for the example script. It made understanding what's going on so much easier. :)

I think the presence of common_submodule in the main repo is actually a red herring. if you remove the last two lines of this stanza:

the outcome is the same.

It looks like "fetch" is smart enough to initialize a submodule when necessary, but not smart enough to do so recursively. If I replace that line with:

  git submodule update --init --recursive

then it works as I'd expect. Likewise, cloning the repository with:

  git clone --recurse-submodules main_repos foo

does what you'd want.

After that, I think "git fetch --recurse-submodules" does what you want, because the submodule repository is already initialized.

I'm not sure to what degree git-fetch intended to support initializing submodules. But it certainly seems like a bug that it handles the top layer but does not recurse (i.e., it should either handle all or none).

Hopefully the commands above at least give you a workaround.

-Peff

Thanks Jeff

You are completely right! It works as I expect if I remember the extra parameter `--recursive` when doing `git submodule update --init --recursive`

Thanks a lot for your feedback! This is really useful! I learned a useful thing today :)

/Jesper

On Thu, Mar 7, 2019 at 7:08 PM Jeff King <peff@peff.net> wrote: