Re: Bug with "git mv" and submodules, and with "git submodule add something --force"

[Stefan Beller <sbeller@google.com>]

On Fri, Oct 19, 2018 at 5:43 AM Juergen Vogl <juergen.vogl@jku.at> wrote:
>
> Hi there,
>
> tested on both, git 2.18 and git 2.19.1:
>
> moving a file with `git mv` from a project to a submodule results in an
> **undefined state** of the local repository.

Luckily we do have a submodule in git.git itself, so we can
try it out here as well (I'll use a separate worktree to not
hose my main repo):

  git worktree add ../testgit && cd ../testgit
  git checkout v2.19.1 && make install
  git --version
  git version 2.19.1
  git submodule update --init
  Cloning into '/home/sbeller/testgit/sha1collisiondetection'...
  Submodule path 'sha1collisiondetection': checked out
'232357eb2ea0397388254a4b188333a227bf5b10'
  git mv cache.h sha1collisiondetection/
  git status
HEAD detached at v2.19.1
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

deleted:    sha1collisiondetection
renamed:    cache.h -> sha1collisiondetection/cache.h

Untracked files:
  (use "git add <file>..." to include in what will be committed)

sha1collisiondetection/.gitignore
sha1collisiondetection/.travis.yml
sha1collisiondetection/LICENSE.txt
sha1collisiondetection/Makefile
sha1collisiondetection/README.md
sha1collisiondetection/lib/
sha1collisiondetection/src/
sha1collisiondetection/test/
sha1collisiondetection/vs2015/

> It breaks up the submodule (it's still in .gitmodules, but not
> accessable via `git submodule`), and is not reversible on local repository.

This seems like what I just did. However reversing can be done via:

  git checkout -f
  git status
HEAD detached at v2.19.1
nothing to commit, working tree clean
  git submodule status
232357eb2ea0397388254a4b188333a227bf5b10 sha1collisiondetection
(stable-v1.0.3-31-g232357e)

So I think it's just "git-mv" that doesn't respect submodule
boundaries, which we would want to address.

The man page of git mv
(https://git-scm.com/docs/git-mv)
actually has a short note about submodules, but that is about
moving *a* submodule not about moving things in and out.

Maybe for now we can do with just an update of the documentation/bugs
section and say we cannot move files in and out of submodules?



>
> Either `git mv submodule/file .`

which is just running the command in reverse, (i.e. swapping
destination and target),
  git mv cache.h sha1collisiondetection/
  git mv sha1collisiondetection/cache.h cache.h
  git status
HEAD detached at v2.19.1
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

deleted:    sha1collisiondetection

Untracked files:
  (use "git add <file>..." to include in what will be committed)

sha1collisiondetection/

which seems like the submodule is gone,

> nor deleting the folder works. For the
> locale repo the submodule is gone.

Yup, that seems to be the case.

> But: trying to add it with `git
> submodule add` also do not work and results in an error message (with
> and without `--force` flag):

Would checkout out a state where the submodule still exists
(such as HEAD) and then running "git submodule update --init"
fix it instead?

>
> $ git submodule add git@github.com:-----------/wiki-public.git public
> --force
> A git directory for 'public' is found locally with remote(s):
>   origin        git@github.com:-----------/wiki-public.git
> If you want to reuse this local git directory instead of cloning again from
>   git@github.com:-----------/wiki-public.git
> use the '--force' option. If the local git directory is not the correct repo
> or you are unsure what this means choose another name with the '--name'
> option.
>
> Therefore, it's in a undefined, broken state.
>
>
> Another bug I've got by testing upper line:
> * --force will be used as folder name * when used in `git submodule add
> git@github.com:someone/some.git --force`:

Yes, the order of arguments is important, the options
(such as --force) goes before the URL and path.

> /usr/libexec/git-core/git-submodule: line 273: cd: --: invalid option
> cd: usage: cd [-L|-P] [dir]
> Unable to checkout submodule '--force'

Gah! We'd need to escape the path after the options,
i.e. cd -- --force
would cd into that directory, but I am unsure if that
is accepted by all shells.

Thanks,
Stefan