Re: [PATCH 12/15] unpack-trees: check if we can perform the operation for submodules

[Stefan Beller <sbeller@google.com>]

On Fri, Feb 17, 2017 at 10:42 AM, Jacob Keller <jacob.keller@gmail.com> wrote:
> On Wed, Feb 15, 2017 at 4:38 PM, Stefan Beller <sbeller@google.com> wrote:
>> +       if (is_active_submodule_with_strategy(ce, SM_UPDATE_UNSPECIFIED))
>
> Here, and in other cases where we use
> is_active_submodule_with_strategy(), why do we only ever check
> SM_UPDATE_UNSPECIFIED? It seems really weird that we're only going to
> check submodules who's strategy is unspecified, when that defaults to
> checkout if I recall correctly? Shouldn't we check both? This applies
> to pretty much everywhere that you call this function that I noticed,
> which is why I removed the context.

I am torn between this.

submodule.<name>.update = {rebase, merge, checkout, none !command}
is currently documented in GIT-CONFIG(1) as

       submodule.<name>.update
           The default update procedure for a submodule. This variable is
           populated by git submodule init from the gitmodules(5) file. See
           description of update command in git-submodule(1).

and in GIT-SUBMODULE(1) as

       update
           [...] can be done in several ways
           depending on command line options and the value of
           submodule.<name>.update configuration variable. Supported update
           procedures are:

           checkout
               [...] or no option is given, and
               submodule.<name>.update is unset, or if it is set to checkout.

So the "update" config clearly only applies to the "submodule update"
command, right?

Well no, "checkout --recurse-submodules" is very similar
to running "submodule update", except with a bit more checks, so you could
think that such an option applies to checkout as well. (and eventually
rebase/merge etc. are supported as well.)

So initially I assumed both "unspecified" as well as "checkout"
are good matches to support in the first round.

Then I flip flopped to think that we should not interfere with these
settings at all (The checkout command does checkout and checkout only;
no implicit rebase/merge ever in the future, because that would be
confusing). So ignoring that option seemed like the way to go.

But ignoring that option is also not the right approach.
What if you have set it to "none" and really *expect* Git to not touch
that submodule?

So I dunno. Maybe it is a documentation issue, we need to spell out
in the man page for checkout that --recurse-submodules is
following one of these models. Now which is the best default model here?

Thanks,
Stefan