Re: [PATCH v2] ls-files: add pathspec matching for submodules

[Brandon Williams <bmwill@google.com>]

On Mon, Sep 19, 2016 at 4:21 PM, Junio C Hamano <gitster@pobox.com> wrote:
>
> As the previous one that used a wrong (sorry) argument is not even
> in 'next' yet, let's pretend that it never happened.  It is OK to
> still keep it and this patch as two separate steps, i.e. a topic
> with two patches in it.
>
> That means that this patch will become 2/2 of a series, and 1/2 is
> rerolled to use submodule_prefix from the get-go, without ever
> introducing output_path_prefix variable, so that many of the above
> lines we won't have to review in 2/2.

Ah ok.  Would you like me to resend the first patch with the desired
change then?

>
>> +     /*
>> +      * Pass in the original pathspec args.  The submodule will be
>> +      * responsible for prepending the 'submodule_prefix' prior to comparing
>> +      * against the pathspec for matches.
>> +      */
>
> Good.
>
>> +     argv_array_push(&cp.args, "--");
>> +     for (i = 0; i < pathspec.nr; ++i)
>> +             argv_array_push(&cp.args, pathspec.items[i].original);
>> +
>
> Please prefer post-increment i++ over pre-increment ++i when writing
> a for(;;) loop, unless there is a strong reason not to (familiarlity
> in C++ is not a good reason).

I had a compiler instructor drill into my head that ++i in a for loop
was faster historically
since it wouldn't have to create a temporary value.  Of course now a days there
probably isn't much (or any) difference between the two.  If post-fix
operators are the
norm in git code then I can try to remember to use them :)

>> +
>> +     if (item->flags & PATHSPEC_ONESTAR) {
>> +             return WM_MATCH;
>> +     } else if (item->magic & PATHSPEC_GLOB) {
>> +             return wildmatch(pattern, string,
>> +                              WM_PATHNAME |
>> +                              (item->magic & PATHSPEC_ICASE ?
>> +                               WM_CASEFOLD : 0),
>> +                              NULL);
>
> Isn't this last one overly tight?  I am wondering about a scenario
> where you have a submodule at "sub/" in the superproject, and "sub/"
> has a "file" at the top of its working tree.  And you do:
>
>         git ls-files --recurse-submodules ':(glob)??b/fi?e'
>
> at the top of the superproject.  The "pattern" would be '??b/fi?e"
> while string would be 'sub', and wildmatch() would not like it, but
> there is no way for this caller to append anything to 'sub' before
> making this call, as it hasn't looked into what paths appear in the
> submodule repository (and it should not want to).  And I think we
> would want it to recurse to find sub/file.  IOW, this looks like a
> false negative we must avoid in this function.  As we cannot afford
> to check if anything that matches 'fi?e' is in the index file of the
> submodule repository, we shouldn't try to match 'fi?e' portion of
> the given pathspec pattern.

good point.  Let me think about this some more.