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

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

[Juergen Vogl]

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.

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

Either `git mv submodule/file .` nor deleting the folder works. For the
locale repo the submodule is gone. But: trying to add it with `git
submodule add` also do not work and results in an error message (with
and without `--force` flag):

$ 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`:

$ git submodule add git@github.com:---/wiki-public.git --force
Cloning into '/home/---/---/---/---/wiki-internal.wiki/--force'...
remote: Enumerating objects: 29, done.
remote: Counting objects: 100% (29/29), done.
remote: Compressing objects: 100% (25/25), done.
remote: Total 29 (delta 5), reused 20 (delta 2), pack-reused 0
Receiving objects: 100% (29/29), 37.03 KiB | 421.00 KiB/s, done.
Resolving deltas: 100% (5/5), done.
/usr/libexec/git-core/git-submodule: line 273: cd: --: invalid option
cd: usage: cd [-L|-P] [dir]
Unable to checkout submodule '--force'

but it creates the `--force` folder:

$ tree
.
├── --force

Best,

Jürgen Vogl

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

[Stefan Beller]

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

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

[Jonathan Nieder]

Stefan Beller wrote:

> 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?

I think we have some existing logic to prevent "git add"-ing a file
within a submodule to the superproject, for example.

So "git mv" should learn the same trick.  And perhaps the trick needs
to be moved down a layer (e.g. into the index API).  Hints?

Thanks,
Jonathan

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

[Junio C Hamano]

Jonathan Nieder <jrnieder@gmail.com> writes:

> Stefan Beller wrote:
>
>> 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?
>
> I think we have some existing logic to prevent "git add"-ing a file
> within a submodule to the superproject, for example.

There is die_path_inside_submodule() that sanity-checks the pathspec
and rejects.  But I think that is done primarily to give an error
message and not strictly necesary for correctness.

The real safety of "git add" is its call to dir.c::fill_directory();
it collects untracked paths that match the pathspec so that they can
be added as new paths, but because it won't cross the module
boundary, you won't get such a path in the index to begin with.

> So "git mv" should learn the same trick.  And perhaps the trick needs
> to be moved down a layer (e.g. into the index API).  Hints?

You would want to be able to remove a submodule and replace it with
a directory, but you can probably do it in two steps, i.e.

	git reset --hard
	git rm --cached sha1collisiondetection
	echo Now a regular dir >sha1collisiondetection/READ.ME
	find sha1collisiondetection ! -type d -print0 | 
	git update-index --add --stdin -z

So from that point of view, forbidding (starting from the same state
of our project) this sequence:

	git reset --hard
	echo Now a regular dir >sha1collisiondetection/READ.ME
	find sha1collisiondetection ! -type d -print0 | 
	git update-index --add --remove --stdin -z

that would nuke the submodule and replace it with a directory within
which there are files would be OK.  Making the latter's default
rejection overridable with ADD_CACHE_OK_TO_REPLACE would also be
fine.

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

[Stefan Beller]

On Sun, Oct 21, 2018 at 7:52 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> Jonathan Nieder <jrnieder@gmail.com> writes:
>
> > Stefan Beller wrote:
> >
> >> 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?
> >
> > I think we have some existing logic to prevent "git add"-ing a file
> > within a submodule to the superproject, for example.
>
> There is die_path_inside_submodule() that sanity-checks the pathspec
> and rejects.  But I think that is done primarily to give an error
> message and not strictly necesary for correctness.

c08397e3aa (pathspec: remove PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE
flag, 2017-05-11) seems to be relevant here, as that factors out the
warning.

> The real safety of "git add" is its call to dir.c::fill_directory();
> it collects untracked paths that match the pathspec so that they can
> be added as new paths, but because it won't cross the module
> boundary, you won't get such a path in the index to begin with.

It would not cross the boundary and fail silently as it would
treat a path into the submodule as a no-op.

> > So "git mv" should learn the same trick.  And perhaps the trick needs
> > to be moved down a layer (e.g. into the index API).  Hints?

Yeah, I think we'd want to teach git-mv about that trick.

Unfortunately git-mv is one of the last remainders of not
properly using pathspecs, and die_path_inside_submodule
expects a pathspec. :-/

> You would want to be able to remove a submodule and replace it with
> a directory, but you can probably do it in two steps, i.e.
>
>         git reset --hard
>         git rm --cached sha1collisiondetection
>         echo Now a regular dir >sha1collisiondetection/READ.ME
>         find sha1collisiondetection ! -type d -print0 |
>         git update-index --add --stdin -z

    "Ignoring path sha1collisiondetection/.git"

Nice!

>
> So from that point of view, forbidding (starting from the same state
> of our project) this sequence:
>
>         git reset --hard
>         echo Now a regular dir >sha1collisiondetection/READ.ME
>         find sha1collisiondetection ! -type d -print0 |
>         git update-index --add --remove --stdin -z
>
> that would nuke the submodule and replace it with a directory within
> which there are files would be OK.  Making the latter's default
> rejection overridable with ADD_CACHE_OK_TO_REPLACE would also be
> fine.

I am having trouble of relating these commands to the original git-mv
across submodule boundaries.

Moving files from the submodule out to the superproject, seems
to fail properly, though having a less-than-optimal error message:

$ git mv sha1collisiondetection/LICENSE.txt .
fatal: not under version control, source=sha1collisiondetection/LICENSE.txt, destination=LICENSE.txt

and moving things inside was the original report, below is a proof of concept
that would yield

./git mv -v cache.h sha1collisiondetection/
fatal: moving across submodule boundaries not supported, source=cache.h, destination=sha1collisiondetection/cache.h

--8<--
Subject: [WIP/PATCH] builtin/mv.c: disallow moving across submodule boundaries

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 builtin/mv.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/builtin/mv.c b/builtin/mv.c
index 80bb967a63..9ec4b2f0a3 100644
--- a/builtin/mv.c
+++ b/builtin/mv.c
@@ -172,7 +172,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 	/* Checking */
 	for (i = 0; i < argc; i++) {
 		const char *src = source[i], *dst = destination[i];
-		int length, src_is_dir;
+		int length, src_is_dir, pos;
 		const char *bad = NULL;
 
 		if (show_only)
@@ -243,6 +243,13 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 		else
 			string_list_insert(&src_for_dst, dst);
 
+		pos = cache_name_pos(dst, strlen(dst));
+		if (pos < 0) {
+			pos = -(pos + 1);
+			if (!S_ISGITLINK(active_cache[pos]->ce_mode))
+				bad = _("moving across submodule boundaries not supported");
+		}
+
 		if (!bad)
 			continue;
 		if (!ignore_errors)
-- 
2.19.0

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

[Junio C Hamano]

Stefan Beller <sbeller@google.com> writes:

>> You would want to be able to remove a submodule and replace it with
>> a directory, but you can probably do it in two steps, i.e.
>>
>>         git reset --hard
>>         git rm --cached sha1collisiondetection
>>         echo Now a regular dir >sha1collisiondetection/READ.ME
>>         find sha1collisiondetection ! -type d -print0 |
>>         git update-index --add --stdin -z
>
>     "Ignoring path sha1collisiondetection/.git"
>
> Nice!

There actually is another possible outcome that anybody following
along must be aware of and be careful about: not even .git directory
exist there, i.e. it is possible that the submodule has never been
init'ed.

So, it is not that nice X-<.