Re: Confusing behavior with ignored submodules and `git commit -a`

> Hi,
>
> In the past few months have noticed some confusing behavior with
> ignored submodules. I finally got around to bisecting this to commit
> 5556808690ea245708fb80383be5c1afee2fb3eb (add, reset: ensure
> submodules can be added or reset).
>
> Here is a demonstration of the problem:
>
> First some repository initialization with a submodule marked as ignored.
>
> $ git init inner && git -C inner commit --allow-empty -m 'inner 1'
> Initialized empty Git repository in /tmp/inner/.git/
> [master (root-commit) ef55bed] inner 1
> $ git init outer && cd outer
> Initialized empty Git repository in /tmp/outer/.git/
> $ git submodule add ../inner
> Cloning into '/tmp/outer/inner'...
> done.
> $ echo 1 > foo.txt && git add foo.txt
> $ git commit -m 'outer 1'
> [master (root-commit) efeb85c] outer 1
>  3 files changed, 5 insertions(+)
>  create mode 100644 .gitmodules
>  create mode 100644 foo.txt
>  create mode 160000 inner
> $ git config submodule.inner.ignore all
> $ git -C inner commit --allow-empty -m 'inner 2'
> [master 7b7f0fa] inner 2
> $ git status
> On branch master
> nothing to commit, working tree clean
> $
>
> Up to here is all expected. However, if I go to update `foo.txt` and
> commit with `git commit -a`, changes to inner get recorded
> unexpectedly. What's worse is the shortstat output of `git commit -a`,
> and the diff output of `git show` give no indication that the
> submodule was changed.
>
> $ echo 2 > foo.txt
> $ git status
> On branch master
> Changes not staged for commit:
>   (use "git add <file>..." to update what will be committed)
>   (use "git checkout -- <file>..." to discard changes in working directory)
>
>         modified:   foo.txt
>
> no changes added to commit (use "git add" and/or "git commit -a")
> $ git commit -a -m 'update foo.txt'
> [master 6ec564c] update foo.txt
>  1 file changed, 1 insertion(+), 1 deletion(-)
> $ git show
> commit 6ec564c15ddae099c71f01750b4c434557525653 (HEAD -> master)
> Author: Michael Forney <mforney@mforney.org>
> Date:   Fri Mar 16 20:18:37 2018 -0700
>
>     update foo.txt
>
> diff --git a/foo.txt b/foo.txt
> index d00491f..0cfbf08 100644
> --- a/foo.txt
> +++ b/foo.txt
> @@ -1 +1 @@
> -1
> +2
> $
>
> There have been a couple occasions where I accidentally pushed local
> changes to ignored submodules because of this. Since they don't show
> up in the log output, it is difficult to figure out what actually has
> gone wrong.
>
> Anyway, since the bisected commit (555680869) only mentions add and
> reset, I'm assuming that this is a regression and not a deliberate
> behavior change. The documentation for submodule.<name>.ignore states
> that the setting should only affect `git status` and the diff family.
> In terms of my expectations, I would go further and say it should only
> affect `git status` and diffs against the working tree.
>
> I took a brief look through the relevant sources, and it wasn't clear
> to me how to fix this without accidentally changing the behavior of
> other subcommands.
>
> Any help with this issue is appreciated!