Re: [PATCH/RFC] Changing submodule foreach --recursive to be depth-first, --parent option to execute command in supermodule as well

[Eric Cousineau <eacousineau@gmail.com>]

On Tue, Mar 5, 2013 at 10:09 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Heiko Voigt <hvoigt@hvoigt.net> writes:
>
>> On Mon, Mar 04, 2013 at 03:00:45PM -0800, Junio C Hamano wrote:
>>> So if you want a single boolean to toggle between the current
>>> behaviour and the other one, it would be --post-order.  But you may
>>> at least want to consider pros and cons of allowing users to give
>>> two separate commands, one for the pre-order visitation (which is
>>> the current "command") and the other for the post-order
>>> visitation. Being able to run both might turn out to be useful.
>>
>> I second that. Having a --post-order=<command/script> switch will give
>> us much more flexibility. For ease of use we could allow --post-order
>> without command to switch the meaning of the main command.
>>
>> So a final solution would have these switches:
>>
>> git submodule foreach ... [--pre-order[=<command>]] [--post-order[=<command>]] [<command>]
>>
>> If only --pre-order without argument is given the command will be
>> executed pre-order. If only --post-order the command will be executed
>> post-order. If both are given its an error and so on...
>>
>> There are some combinations we would need to catch as errors but this
>> design should allow a step by step implementation:
>>
>>       1. just the --post-order switch
>>       2. --post-order with argument switch
>>       3. --pre-order (including argument) for symmetry of usage
>
> Yeah, I think I can agree with that direction, and Eric's patch
> could be that first step of the three-step progression, without
> painting us into a corner we cannot get out of when we want to
> advance to 2 and 3 later.
>
> I was more interested in the design aspect and I didn't look at the
> actual patch text, though.

Would these be the correct behaviors of Heiko's implementation?

git submodule foreach # Empty command, pre-order
git submodule foreach --pre-order # Same behavior
git submodule foreach --post-order # Empty command, post-order
git submodule foreach 'frotz' # Do 'frotz' pre-order in each submodule
git submodule foreach --post-order 'frotz' # Do 'frotz' post-order in
each submodule
git submodule foreach --pre-order='frotz' --post-order='shimmy' # Do
'frotz' pre-order and 'shimmy' post-order in each submodule
git submodule foreach --post-order='shimmy' 'frotz' # Invalid usage of
the command
git submodule foreach --post-order --pre-order #

It should not be too hard to have this functionality affect the
--include-super command as well.

And would it be worth it to abstract this traversal to expose it to
other commands, such as 'update', to consolidate the code some?
I think Imram was doing something like that in his post.

- Eric