Re: [PATCH RFC] diff: add SUBMODULE_DIFF format to display submodule diff

From: Stefan Beller <sbeller@google.com>
Date: Aug 9, 2016, 23:10 UTC
Message-ID: <CAGZ79kZbHAsxf9G-8=nz3o_zOMNFPa=kSphdo=4zLq97jycbYg@mail.gmail.com>
In-Reply-To: <CA+P7+xqnALzwkgLXrP57BUtFGaxGudAEG7cmGTakP47ofFEjHQ@mail.gmail.com>

On Tue, Aug 9, 2016 at 3:56 PM, Jacob Keller <jacob.keller@gmail.com> wrote:

Show 9 quoted lines

>>> +
>>> +       if (strbuf_read(buf, cp.out, 0) < 0)
>>
>> So we keep the whole diff in memory
>> I don't know much about the diff machinery, but I thought
>> the rest of the diff machinery just streams it out?
>
> Yea, but I can't figure out how to do that. Is there an easy way to
> stream chunks from the pipe straight into the file?

Maybe, roughly:

    cp.stdout = -1;
    start_command(&cp);
    do {
        int r = xread(cp.stdout, buf, MAX_IO_SIZE);
    } while (r >=0);
    finish_command(&cp);

xread does use a poll() for you so it is not active polling, but only reading when data is available.

Show 8 quoted lines

>>
>> When not checked out, we can invoke the diff command
>> in .git/modules/<name> as that is the git dir of the submodule,
>> i.e. operating diff with a bare repo?
>
> We can actually do this every time. How would you pass that in a
> child_process? I don't think it's "dir" but instead passing
> "--git-dir" somehow?

git -C $GIT_DIR diff --relative ${superprojects ce->name}

with $GIT_DIR = ${SUPERPROJECTS GITDIR + modules/<name>/ with name to be looked as submodule_from_path(ce->name) and then taking `name` from the submodule struct)

Thanks, Stefan