Re: [PATCH] submodule: do not pass null OID to setup_revisions

[Jonathan Tan <jonathantanmy@google.com>]

On Thu, 24 May 2018 16:07:49 -0700
Stefan Beller <sbeller@google.com> wrote:

> Hi Jonathan,
> 
> On Thu, May 24, 2018 at 1:47 PM, Jonathan Tan <jonathantanmy@google.com> wrote:
> > If "git pull --recurse-submodules --rebase" is invoked when the current
> > branch and its corresponding remote-tracking branch have no merge base,
> > a "bad object" fatal error occurs. This issue was introduced with commit
> > a6d7eb2c7a ("pull: optionally rebase submodules (remote submodule
> > changes only)", 2017-06-23), which also introduced this feature.
> 
> Ok, what should happen instead?

Just for there not to be this "bad object" error.

> > This is because cmd_pull() in builtin/pull.c thus invokes
> > submodule_touches_in_range() with a null OID as the first parameter.
> > Ensure that this case works, and document what happens in this case.
> 
> By documenting you mean adding a test, i.e. documenting it for the
> developers, not the users.

I also updated the submodule.h file, but yes, it is for the developers.
I'll change the commit message to make this more clear if I need a
reroll.

> I inserted a test_pause here and inspect child:
> * the submodule is the same as in parent, so this patch is
>   just testing it works with submodules the same?
> * No, the submodule is not cloned into the child
>   at all. So we do not know what do do with the submodule.

Yes, this test doesn't do much. I just wanted to make sure that
submodule_touches_in_range() could be called without encountering this
unrelated error.

(Incidentally, we might want to add tests for the "cannot rebase with
locally recorded submodule modifications", but I haven't looked into
that.)

> However this patch is about making sure the superproject
> works out well, without this patch we'd have
> $ git -C child pull --recurse-submodules --rebase
> fatal: bad object 0000000000000000000000000000000000000000
> which is to be avoided.
> 
> Yes I think this is the best way to fix the issue, I thought for some time that
> could first check if submodules are initialzed or active, but these
> are checks are done afterwards, so this is ok.
> 
> Reviewed-by: Stefan Beller <sbeller@google.com>

Thanks!