Re: [PATCH v3 2/2] diff: add SUBMODULE_DIFF format to display submodule diff

> Jacob Keller <jacob.e.keller@intel.com> writes:
>
>> @@ -2305,6 +2311,15 @@ static void builtin_diff(const char *name_a,
>>       struct strbuf header = STRBUF_INIT;
>>       const char *line_prefix = diff_line_prefix(o);
>>
>> +     diff_set_mnemonic_prefix(o, "a/", "b/");
>> +     if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
>> +             a_prefix = o->b_prefix;
>> +             b_prefix = o->a_prefix;
>> +     } else {
>> +             a_prefix = o->a_prefix;
>> +             b_prefix = o->b_prefix;
>> +     }
>> +
>
> Hmph, is it safe to raise this when SUBMODULE_DIFF is not in effect?
> Not objecting, just asking.

>
>>       if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
>> ...
>> +     } else if (DIFF_OPT_TST(o, SUBMODULE_DIFF) &&
>
> This makes clear that SUBMODULE_LOG and SUBMODULE_DIFF should not be
> independent bits in the diff-opt flag word.  We used to run
> something like "log --oneline --left-right A...B" and your new code
> runs "diff A B", but the next month somebody else would want to do
> "log -p --left-right A...B" or something else, and they are clearly
> mutually exclusive.

>
>> diff --git a/diff.h b/diff.h
>> index 6a91a1139686..65df44b1fcba 100644
>> --- a/diff.h
>> +++ b/diff.h
>> @@ -69,7 +69,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
>>  #define DIFF_OPT_FIND_COPIES_HARDER  (1 <<  6)
>>  #define DIFF_OPT_FOLLOW_RENAMES      (1 <<  7)
>>  #define DIFF_OPT_RENAME_EMPTY        (1 <<  8)
>> -/* (1 <<  9) unused */
>> +#define DIFF_OPT_SUBMODULE_DIFF      (1 <<  9)
>
> So I'd really prefer not to see this change; instead, we should move
> in the direction where we _REMOVE_ DIFF_OPT_SUBMODULE_LOG from these,
> and introduce an enum to hold "how would we show submodule changes"
> in the diff_options structure.