Re: Unable to de-init stubborn submodule

[Stefan Beller <sbeller@google.com>]

On Thu, Jan 11, 2018 at 6:12 AM, Ævar Arnfjörð Bjarmason
<avarab@gmail.com> wrote:
> What if we wanted to drop sha1collisiondetection/ as a submodule and
> replace it with a copy of what's now in sha1dc/? I ran into this with
> another project, but here's a way to reproduce it on git.git:
>
>     (
>         rm -rf /tmp/git &&
>         git clone git@github.com:git/git.git /tmp/git
>         cd /tmp/git &&
>         git tag nuke-before &&
>         git submodule update --init &&

At this point
    $ tail -n 3 .git/config
    [submodule "sha1collisiondetection"]
        active = true
        url = https://github.com/cr-marcstevens/sha1collisiondetection.git


>         git rm -r .gitmodules sha1collisiondetection &&

no need to delete the .gitmodules here. Git detects you're deleting a submodule
and adjusts the .gitmodules file (it is empty after just "git rm sha1coll...")

>         git commit -m"Nuke sha1dc submodule" &&
>         cp -Rvp sha1dc sha1collisiondetection &&
>         git add sha1collisiondetection &&
>         git commit -m"Now it's not a submodule" &&
>         git tag nuke-after &&
>         git reset --hard nuke-before &&

As bmwill said, you may want to reset with --recurse-submodules here,
"git ls-tree HEAD |grep sha1c" will show commit and "git status" thinks
everything is fine on disk. I have no suspicion to believe otherwise.
But we digress, you chose to not use that flag.

>         git submodule update --init && # skip this and the below won't fail
>         git reset --hard nuke-after && # Emulate someone doing a pull

$ git reset --hard nuke-after
warning: unable to rmdir 'sha1collisiondetection': Directory not empty
HEAD is now at f683a1b81 Now it's not a submodule
$ git reset --hard nuke-after --recurse-submodules
HEAD is now at f683a1b81 Now it's not a submodule


>         git ls-tree HEAD | grep sha1collisiondetection && # OK, shows "tree" not "commit"
>         test $(git rev-parse HEAD) == $(git -C sha1collisiondetection/ log -1 --pretty=format:%H) && echo OK || echo WTF
>     )
>
> This results in a really bizarre state where according to ls-tree
> sha1collisiondetection is a tree at the current commit:
>
>     040000 tree 81583289d96bdde4b366c243ab524ea28d895ea5    sha1collisiondetection
>
> But git still believes there's a submodule there for some reason, and
> shows the log for the upstream sha1collisiondetection project:
>
>     git -C sha1collisiondetection/ log -1

(A)
That is because the reset without flag do touch submodules kept the
submodule in place and the -C in this command tells git to cd into that
directory, (which is the submodule, an 'independent' repo) and shows the
log of said repo.

>     commit 19d97bf (HEAD, origin/master, origin/HEAD, master)
>     Merge: 3f14d1b c93f0b4
>     Author: Dan Shumow <shumow@gmail.com>
>     Date:   Sat Jul 1 12:36:15 2017 -0700
>
>         Merge pull request #37 from avar/fixup-pull-request-34
>
>         Fix endian detection logic for Sparc, little endian BSD etc.
>
> Doing:
>
>     git submodule deinit sha1collisiondetection

Doing this after you reset to nuke-after, there are no submodules from
the superprojects point of view, hence no submodule is touched/modified. :/
(There just happens to be a stray repository at a place where we'd want
to have a tree).

> Does nothing to help, then I thought it might be:
>
>     git config -f .git/config -l|grep ^submodule
>     submodule.sha1collisiondetection.active=true
>     submodule.sha1collisiondetection.url=https://github.com/cr-marcstevens/sha1collisiondetection.git
>
> But running:
>
>     git config --remove-section submodule.sha1collisiondetection

This made the submodule not active any more, (note that at the current
tree there
is no submodule to begin with... so what effect to we want here?)

> Doesn't help either, neither does removing the index:
>
>     rm .git/index &&
>     git reset --hard
>
> If you then do:
>
>     rm -rf .git/modules

Getting out the big hammer, eh?

instead of deleting the submodules git repo, remove its worktree:

    rm -rf sha1collisiondetection

(This is best done at time (A) above)

>
> You'll get this error:
>
>     git -C sha1collisiondetection/ log -1
>     fatal: Not a git repository: /tmp/git/sha1collisiondetection/../.git/modules/sha1collisiondetection
>
> But I can't see what's still referencing it.

$ls -la /tmp/git/sha1collisiondetection
...
-rw-r--r--  1 sbeller eng    47 Jan 11 10:02 .git
...
$ cat sha1collisiondetection/.git
gitdir: ../.git/modules/sha1collisiondetection

This is a crucial file, telling you there is a repo with the worktree
at the place where
.git lives and the git dir is at the location indicated (which you removed)

> This problem is avoided if, as noted with a comment I skip:
>
>     git submodule update --init
>
> But I shouldn't need to remember to de-init a submodule before moving to
> a new commit that doesn't have it, least I end up in some seemingly
> unrecoverable state.
>
> Am I missing something obvious here?

The "git submodule update/init/deinit" is a "raw" command,
(not to be confused with plumbing, I just made up "raw commands" ;)
that is very good to deal with submodules, but that tool has sharp edges.
Try this:

  $ git clone --recurse-submodules=. git@github.com:git/git.git testgit
  $ cd testgit/
  $ git config --list |grep submod
submodule.active=.
submodule.sha1collisiondetection.url=https://github.com/cr-marcstevens/sha1collisiondetection.git
  $ git config submodule.recurse true
  $ git tag before-nuke
  $ git rm sha1collisiondetection/
  rm 'sha1collisiondetection'
  $ git commit -a -m delete_sub
  $ git tag after-nuke
  $ git checkout before-nuke
  $ git status # and more checks
  $ git checkout after-nuke
  $ git status # and more checks