Re: My Git Dev Blog - Week 9

From: Kaartic Sivaraam <kaartic.sivaraam@gmail.com>
Date: Jul 19, 2021, 02:58 UTC
Message-ID: <a8122438-8d8b-9e7d-d66a-dc6eff7a0817@gmail.com>
In-Reply-To: <09edd920-e9ef-f8f9-79e6-d27badd2e5a6@gmail.com>

Hi Atharva and all,

On 19/07/21 12:49 am, Kaartic Sivaraam wrote:

Show 10 quoted lines

> 
> On 18/07/21 5:29 pm, Atharva Raykar wrote:
> 
>> Passing the superprefix explicitly
> 
> My gut instinct tells me we could get away without having to go this way but
> I haven't yet been able to figure out how. How 'prefix', 'super-prefix' and
> 'recursive-prefix' is still puzzling me. In case anyone has knowledge about
> this please chime in and enlighten us. It would be very helpful.
>

I just noticed I was short and unhelpful here. To expand on what information would be helpful on this respect, here's a snippet of a private e-mail I sent which I've tweaked a little to make it relevant for the list audience:

-- 8< --

Show 28 quoted lines

>> Problem:
>> -------
>> I cannot get 'submodule update --init --recursive' to work properly.
>> 
>> Cause:
>> -----
>> The paths get malformed in my first implementation[1] because I am not able
>> to transfer the git 'superprefix' to the 'init_submodule_cb' callback with the
>> current interface. The superprefix is required by the
>> 'get_submodule_displaypath()' function to create the correct display path.
>>
>> Thus, t406.5 fails.
>> 
>> For more details on this and the exact error,
>> cf.: https://atharvaraykar.me/gitnotes/week8#path-pains
>>
>> [ snip ]
>>
>> The link at [1] is the one where it fails only one test in my machine.
>>
>> [ snip ]
>>
>> This version does *not* start a subprocess for running init before the
>> update. The relevant lines for this are here:
>> https://github.com/tfidfwastaken/git/blob/7ad995f465072b60a8c33e51c4f91d08ee3d2484/builtin/submodule--helper.c#L3325-L3344
>>
>> [1]: https://github.com/tfidfwastaken/git/commits/submodule-helper-update-1b
>>

I took a look at this. I'm not able to find the exact issue but my gut instinct tells me it has something to do with how prefix, super-prefix and recursive-prefix are handled before and after the conversion. To be more specific, I'm having doubts about whether the following code snippet[4] in shell ...

     prefix=$(git submodule--helper relative-path "$prefix$sm_path/" "$wt_prefix")
     wt_prefix=
     sanitize_submodule_env
     cd "$sm_path" &&
     eval cmd_update

... has been properly converted to C. Particularly, the fact that recursive calls to 'cmd_update' is made in the existing shell implementation in case '--recusive' is passed needs to be observed well. This would subsequently result in multiple calls to 'cmd_init' with different 'prefix' and 'wt_prefix' values. So, that needs to be observed well too.

I have not been able to get a complete picture of this myself. I'll try to take better look later and see if I could get anything.

Note that this could also be me just not being able to get a proper picture of it. Just wanted to share it in case others are able to get any ideas or able to think of a possible cause.

[4]: https://github.com/git/git/blob/abb21c7263616f01c5e950861a29279ab21cb02f/git-submodule.sh#L654-L658 -- >8 --

I hope that gives a better idea about what kind of information would be helpful. Kindly let me know if it doesn't.

Atharva,

In the meanwhile, I think you could continue polishing your attempted solution and preparing to send it to the list. I'll try to dig more on my gut instinct and let you know if I get anything. If you have some free time left after polishing your series, you could try digging into it too :)

-- 
Sivaraam