Re: [PATCH 7/9] submodule: fetch in submodules git directory instead of in worktree

[Jonathan Tan <jonathantanmy@google.com>]

> > Why does GIT_DIR need to be set? Is it to avoid subcommands recursively
> > checking the parent directories in case the CWD is a malformed Git
> > repository? If yes, maybe it's worth adding a comment.
> 
> It is copying the structure from prepare_submodule_repo_env,
> specifically 10f5c52656 (submodule: avoid auto-discovery in
> prepare_submodule_repo_env(), 2016-09-01), which sounds
> appealing (and brings real benefits for the working directory),
> but I have not thought about this protection for the git dir.
> 
> Maybe another approach is to not set the cwd for the child process
> and instead point GIT_DIR_ENVIRONMENT only to the right
> directory.
> 
> Then the use of GIT_DIR_ENVIRONMENT is obvious and
> is not just for protection of corner cases.
> 
> However I think this protection is really valuable for the
> .git dir as well as the submodule may be broken and we do not
> want to end up in an infinite loop (as the discovery would find
> the superproject which then tries to recurse, again, into the
> submodule with the broken git dir)
> 
> When adding the comment here, we'd also want to have
> the comment in prepare_submodule_repo_env, which
> could be its own preparation commit.

I agree with the protection. As for the preparation commit, I don't
think it's always the code author's responsibility to tidy up the
surrounding code, but since you're adding an identical comment here,
it's probably worth it to add the comment there too.

> > This is the significant thing that this patch does more - an unskipped
> > submodule is now something that either passes the checks in
> > repo_submodule_init() or the checks in repo_init(), which seems to be
> > stricter than the current check that ".git" points to a directory or is
> > one. This means that we skip certain broken repositories, and this
> > necessitates a change in the test.
> 
> I see. However there is no change in function, the check in repo_init
> (or repo_submodule_init) is less strict than the check in the child process.
> So if there are broken submodule repositories, the difference of this
> patch is the layer at which it is caught, i.e. we would not spawn a child
> that fails, but skip the submodule.
> 
> Thinking of that, maybe we need to announce that in get_next_submodule

The consequence of getting caught changes, though. Currently,
spf->result is set to 1 whenever a child process fails. But in this
patch, some of these repositories would be entirely skipped, meaning
that no child process is run, and spf->result is never modified.

> > I think we should be more particular about what we're allowed to skip -
> > in particular, maybe if we're planning to skip this submodule, its
> > corresponding directory in the worktree (if one exists) needs to be
> > empty.
> 
> If the working tree directory is empty for that submodule, it means
> it is likely not initialized. But why would we use that as a signal to
> skip the submodule?

What I meant was: if empty, skip it completely. Otherwise, do the
repo_submodule_init() and repo_init() thing, and if they both fail, set
spf->result to 1, preserving existing behavior.