bug: git submodule add fails when .git is a symlink

bug: git submodule add fails when .git is a symlink

[Joey Hess]

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        git init gitdir
        mkdir worktree
        cd worktree
        ln -s ../gitdir/.git .git
        git submodule add /any/git/repo sub

        fatal: Could not chdir to '../../../sub': No such file or directory

Fairly sure this is a bug..

-- 
see shy jo

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Re: bug: git submodule add fails when .git is a symlink

[Stefan Beller]

On Tue, Mar 1, 2016 at 12:42 PM, Joey Hess <id@joeyh.name> wrote:
>         git init gitdir
>         mkdir worktree
>         cd worktree
>         ln -s ../gitdir/.git .git
>         git submodule add /any/git/repo sub
>
>         fatal: Could not chdir to '../../../sub': No such file or directory
>
> Fairly sure this is a bug..

Which version(s) of Git do you use?

Re: bug: git submodule add fails when .git is a symlink

[Stefan Beller]

On Tue, Mar 1, 2016 at 1:39 PM, Stefan Beller <sbeller@google.com> wrote:
> On Tue, Mar 1, 2016 at 12:42 PM, Joey Hess <id@joeyh.name> wrote:
>>         git init gitdir
>>         mkdir worktree
>>         cd worktree
>>         ln -s ../gitdir/.git .git
>>         git submodule add /any/git/repo sub
>>
>>         fatal: Could not chdir to '../../../sub': No such file or directory
>>
>> Fairly sure this is a bug..
>
> Which version(s) of Git do you use?

To elaborate on that: Starting in 2.7 parts of the submodule stuff
has been rewritten in C, in 2.8 even more and there is more in flight for
 > 2.8.

However your bug is also to be found in 2.6, which doesn't contain any
recent rewrites, so it is a rather long standing bug, I would presume.

As a workaround for now:

    echo "gitdir: ../gitdir/.git" > .git

instead of the symbolic link in your example (works in 2.6 and also in
2.8.0-rc0)

Thanks,
Stefan

Re: bug: git submodule add fails when .git is a symlink

[Joey Hess]

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Stefan Beller wrote:
> To elaborate on that: Starting in 2.7 parts of the submodule stuff
> has been rewritten in C, in 2.8 even more and there is more in flight for
>  > 2.8.
> 
> However your bug is also to be found in 2.6, which doesn't contain any
> recent rewrites, so it is a rather long standing bug, I would presume.

Yes, I saw it with 2.7.0, but I think the user who reported it was on
2.6.

> As a workaround for now:
> 
>     echo "gitdir: ../gitdir/.git" > .git

Not an option in our particular situation, unfortunately.

I wonder if the miscalculated ../../../somedir could cause git to access
files outside the git repos?

-- 
see shy jo

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Re: bug: git submodule add fails when .git is a symlink

[Junio C Hamano]

Stefan Beller <sbeller@google.com> writes:

> On Tue, Mar 1, 2016 at 12:42 PM, Joey Hess <id@joeyh.name> wrote:
>>         git init gitdir
>>         mkdir worktree
>>         cd worktree
>>         ln -s ../gitdir/.git .git
>>         git submodule add /any/git/repo sub
>>
>>         fatal: Could not chdir to '../../../sub': No such file or directory
>>
>> Fairly sure this is a bug..
>
> Which version(s) of Git do you use?

A more pertinent question may be which version of Git did the above
ever work, I guess.  We fairly liberally chdir around and I do not
think we deliberately avoid assuming that "cd .git && cd .." might
not come back to the original directory, for example, so I wouldn't
be surprised if it never worked.

Re: bug: git submodule add fails when .git is a symlink

[Joey Hess]

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Junio C Hamano wrote:
> A more pertinent question may be which version of Git did the above
> ever work, I guess.  We fairly liberally chdir around and I do not
> think we deliberately avoid assuming that "cd .git && cd .." might
> not come back to the original directory, for example, so I wouldn't
> be surprised if it never worked.

IIRC git used symlinks for .git in submodules before version 1.7.8, so I
guess that older versions supported that pretty well.

This one case is the only time I've seen a symlink for .git present a
problem so far.

-- 
see shy jo

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Re: bug: git submodule add fails when .git is a symlink

[Jeff King]

On Tue, Mar 01, 2016 at 07:17:20PM -0400, Joey Hess wrote:

> Junio C Hamano wrote:
> > A more pertinent question may be which version of Git did the above
> > ever work, I guess.  We fairly liberally chdir around and I do not
> > think we deliberately avoid assuming that "cd .git && cd .." might
> > not come back to the original directory, for example, so I wouldn't
> > be surprised if it never worked.
> 
> IIRC git used symlinks for .git in submodules before version 1.7.8, so I
> guess that older versions supported that pretty well.
> 
> This one case is the only time I've seen a symlink for .git present a
> problem so far.

Fortunately you provided a simple reproduction case, so it is easy to
bisect. It did work in v1.7.8, and broke in d75219b (submodules: always
use a relative path from gitdir to work tree, 2012-03-04). Not
surprising, I guess. It presumably worked before only because we were
using absolute paths.

-Peff

Re: bug: git submodule add fails when .git is a symlink

[Stefan Beller]

On Wed, Mar 2, 2016 at 12:49 AM, Jeff King <peff@peff.net> wrote:
> On Tue, Mar 01, 2016 at 07:17:20PM -0400, Joey Hess wrote:
>
>> Junio C Hamano wrote:
>> > A more pertinent question may be which version of Git did the above
>> > ever work, I guess.  We fairly liberally chdir around and I do not
>> > think we deliberately avoid assuming that "cd .git && cd .." might
>> > not come back to the original directory, for example, so I wouldn't
>> > be surprised if it never worked.
>>
>> IIRC git used symlinks for .git in submodules before version 1.7.8, so I
>> guess that older versions supported that pretty well.
>>
>> This one case is the only time I've seen a symlink for .git present a
>> problem so far.
>
> Fortunately you provided a simple reproduction case, so it is easy to
> bisect. It did work in v1.7.8, and broke in d75219b (submodules: always
> use a relative path from gitdir to work tree, 2012-03-04). Not
> surprising, I guess. It presumably worked before only because we were
> using absolute paths.

So I was looking into this bug again, as it was linked from another bug report.

fatal: Could not chdir to '../../../sub': No such file or directory

sounds like a path issue with the prefix thing.

Using the " echo "gitdir: ../gitdir/.git" > .git" workaround does still work,
I'll see if there is another way to fix it with actual links.


>
> -Peff
> --
> To unsubscribe from this list: send the line "unsubscribe git" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: bug: git submodule add fails when .git is a symlink

[Stefan Beller]

On Wed, Apr 20, 2016 at 9:41 AM, Stefan Beller <sbeller@google.com> wrote:
> On Wed, Mar 2, 2016 at 12:49 AM, Jeff King <peff@peff.net> wrote:
>> On Tue, Mar 01, 2016 at 07:17:20PM -0400, Joey Hess wrote:
>>
>>> Junio C Hamano wrote:
>>> > A more pertinent question may be which version of Git did the above
>>> > ever work, I guess.  We fairly liberally chdir around and I do not
>>> > think we deliberately avoid assuming that "cd .git && cd .." might
>>> > not come back to the original directory, for example, so I wouldn't
>>> > be surprised if it never worked.
>>>
>>> IIRC git used symlinks for .git in submodules before version 1.7.8, so I
>>> guess that older versions supported that pretty well.
>>>
>>> This one case is the only time I've seen a symlink for .git present a
>>> problem so far.
>>
>> Fortunately you provided a simple reproduction case, so it is easy to
>> bisect. It did work in v1.7.8, and broke in d75219b (submodules: always
>> use a relative path from gitdir to work tree, 2012-03-04). Not
>> surprising, I guess. It presumably worked before only because we were
>> using absolute paths.
>
> So I was looking into this bug again, as it was linked from another bug report.
>
> fatal: Could not chdir to '../../../sub': No such file or directory
>
> sounds like a path issue with the prefix thing.
>
> Using the " echo "gitdir: ../gitdir/.git" > .git" workaround does still work,
> I'll see if there is another way to fix it with actual links.

So I debugged into that using a test case

test_expect_success 'submodules are not confused by linked gitdir' '
        git init gitdir &&
        mkdir worktree &&
        (
                cd worktree &&
                #echo "gitdir: ../gitdir/.git" >.git &&
                ln -s ../gitdir/.git .git &&
                test_pause &&
                git submodule add ../ sub &&
                test_pause
        ) &&
        test_pause &&
        git status
'

My observation: the error comes up in `git submodule add`,
which consists of 2 parts: the cloning and then the checkout.
The cloning works fine using the new "submodule--helper update-clone",
the checkout however breaks. So in your original test case you can go
into the submodule and run

    git checkout -f -q

and you'll get the error message

    fatal: Could not chdir to '../../../sub': No such file or directory

Looking at sub/.git:

    $ cat .git
    gitdir: ../.git/modules/sub
    $ ls ../.git/modules/sub
    HEAD  branches config description  hooks  info  logs objects
packed-refs  ref

so that gitlink of the submodule works just fine. The problem is `git checkout`
or any other core command (I tested with `git status`) doesn't like
the gitlink pointing to a directory which is symlinked.

I think the issue is a wrongly configured "core.worktree"
in gitdir/.git/modules/sub/config which contains the "../../../sub".

So I think the fix needs to be in the vicinity of
builtin/submodule--helper.c:module_clone
near the end of the function, where core.worktree is set.

Thanks,
Stefan


>
>
>>
>> -Peff
>> --
>> To unsubscribe from this list: send the line "unsubscribe git" in
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