Re: [PATCH v5 9/9] submodule: support reading .gitmodules when it's not in the working tree

[Stefan Beller <sbeller@google.com>]

On Mon, Sep 24, 2018 at 3:20 AM Antonio Ospite <ao2@ao2.it> wrote:

> > The third call, however, looks at the nested submodule at
> > 'submodule/sub', which doesn't contain a '.gitmodules' file.  So this
> > function goes on with the second condition and calls
> > get_oid(GITMODULES_INDEX, &oid), which then appears to find the blob
> > in the _superproject's_ index.
> >
>
> You are correct.
>
> This is a limitation of the object store in git, there is no equivalent
> of get_oid() to get the oid from a specific repository and this affects
> config_with_options too when the config source is a blob.

Not yet, as there is a big push to pass-through an object-store object
or similar recently and rely less on global variables.
I am not sure I get to this code, though.

> This does not affect commands called via "git -C submodule_dir cmd"
> because in that case the chdir happens before the_repository is set up,
> for instance "git-submodule $SOMETHING --recursive" commands seem to
> change the working directory before the recursion.

For this it may be worth looking into the option
       --super-prefix=<path>
  Currently for internal use only. Set a prefix which gives a
  path from above a repository down to its root. One use is
  to give submodules context about the superproject that
  invoked it.

the whole motion of moving to in-process deprecates this clunky
API to pass around strings to subprocesses.

> The test suite passes even after removing repo_read_gitmodules()
> entirely from builtin/grep.c, but I am still not confident that I get
> all the implication of why that call was originally added in commit
> f9ee2fcdfa (grep: recurse in-process using 'struct repository',
> 2017-08-02).

If you checkout that commit and remove the call to repo_read_gitmodules
and then call git-grep in a superproject with nested submodules, you
get a segfault.

On master (and deleting out that line) you do not get the segfault,
I think praise goes to ff6f1f564c4 (submodule-config: lazy-load a
repository's .gitmodules file, 2017-08-03) which happened shortly
after f9ee2fcdfa.

It showcased that it worked by converting ls-files, but left out grep.

So I think based on ff6f1f564c4 it is safe to remove all calls to
repo_read_gitmodules.

> Anyways, even if we removed the call we would prevent the problem from
> happening in the test suite, but not in the real world, in case non-leaf
> submodules without .gitmodules in their working tree.

Quite frankly I think grep was just overlooked in review of
https://public-inbox.org/git/20170803182000.179328-14-bmwill@google.com/

Stefan