let git grep consider sub projects

> How can I teach 'git grep $string' to also consider subprojects?
>
> The build system of xen.git clones 4 other trees into a directory in its
> source tree during build. It would be nice if my 'git grep' searches
> also in these cloned subdirs. Somehow there must be some knowledge
> because 'git clean -dfx' leaves them alone, while 'git clean -dffx'
> wipes everything.
>
> Olaf
>
> PS: Sometimes I miss a 'git clean -dfx --also-sub-repos' useful to
> really clean everything before starting over.

> Olaf Hering <olaf@aepfle.de> writes:
>
>> How can I teach 'git grep $string' to also consider subprojects?
>>
>> The build system of xen.git clones 4 other trees into a directory in its
>> source tree during build. It would be nice if my 'git grep' searches
>> also in these cloned subdirs. Somehow there must be some knowledge
>> because 'git clean -dfx' leaves them alone, while 'git clean -dffx'
>> wipes everything.
>>
>> Olaf
>>
>> PS: Sometimes I miss a 'git clean -dfx --also-sub-repos' useful to
>> really clean everything before starting over.
>
> Is "submodule foreach" under-advertised or with less than adequate
> features?

> On 7 October 2014 20:25, Junio C Hamano <gitster@pobox.com> wrote:
>> Olaf Hering <olaf@aepfle.de> writes:
>>
>>> How can I teach 'git grep $string' to also consider subprojects?
>>>
>>> The build system of xen.git clones 4 other trees into a directory in its
>>> source tree during build. It would be nice if my 'git grep' searches
>>> also in these cloned subdirs. Somehow there must be some knowledge
>>> because 'git clean -dfx' leaves them alone, while 'git clean -dffx'
>>> wipes everything.
>>>
>>> Olaf
>>>
>>> PS: Sometimes I miss a 'git clean -dfx --also-sub-repos' useful to
>>> really clean everything before starting over.
>>
>> Is "submodule foreach" under-advertised or with less than adequate
>> features?
>
> It sounds like in these use cases, you would want the commands to run
> on all the submodules but also in the parent repo, am I wrong in
> thinking that git submodule foreach does only the former part? So you
> would either need to make a wrapper thing yourself or run the command
> twice.

> In the first case with the git grep, I can also imagine that with some
> nontrivial patterns, having to quote the metacharacters not only once,
> but twice, can be a significant annoyance. Eg, first protect it from
> git submodule foreach parsing it, and then from the shell running the
> individual commands.

> On Wed, Oct 08, Jens Lehmann wrote:
>
>>     git foo && git submodule foreach --recursive git foo
>
> Looks like a submodule is yet another thing, or I have to learn what a
> submodule is:
>
> olaf@bax:~/xen $ find . -name .git
> ./.git
> ./tools/qemu-xen-dir-remote/.git
> ./tools/qemu-xen-traditional-dir-remote/.git
> ./tools/firmware/seabios-dir-remote/.git
> olaf@bax:~/xen $ git submodule foreach --recursive git show
> olaf@bax:~/xen $
>
> xen does essentially 'git clone $url1 dir/url1-dir;git clone $url2
> dir/url2-dir'. So the top level .git does not really know about
> dir/*-dir.

> Okay, I just checked that xen doesn't use submodules but uses simple
> embedded repos ignored by the .gitignore file. From a quick glance
> it looks like handling the sub projects is scripted in the Makefiles.
> This is perfectly fine, but then you can't really expect git commands
> to know about these sub projects. Or am I missing something?