On Wed, Jun 21, 2017 at 1:05 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Stefan Beller <sbeller@xxxxxxxxxx> writes:
>
>> static void emit_add_line(const char *reset,
>> struct emit_callback *ecbdata,
>> const char *line, int len)
>> {
>> - emit_line_checked(reset, ecbdata, line, len,
>> - DIFF_FILE_NEW, WSEH_NEW, '+');
>> + unsigned flags = WSEH_NEW | ecbdata->ws_rule;
>> + if (new_blank_line_at_eof(ecbdata, line, len))
>> + flags |= DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF;
>> +
>> + emit_diff_symbol(ecbdata->opt, DIFF_SYMBOL_PLUS, line, len, flags);
>> }
>
> This is a bit unsatisfactory that the original code didn't even have
> to make a call to new_blank_line_at_eof() at all when we know we are
> not checking for / coloring whitespace errors, but the function is
> called unconditionally in the new code.
We could check if we do colored output here, I think'll just do that for now,
but on the other hand this becomes a maintenance nightmare when we
rely on these flags in the future e.g. for "machine parse-able coloring"
and would markup according to the flags strictly. I guess we can fix it then.
>
>> diff --git a/diff.h b/diff.h
>> index 5be1ee77a7..8483ca0991 100644
>> --- a/diff.h
>> +++ b/diff.h
>> @@ -148,9 +148,9 @@ struct diff_options {
>> int abbrev;
>> int ita_invisible_in_index;
>> /* white-space error highlighting */
>> -#define WSEH_NEW 1
>> -#define WSEH_CONTEXT 2
>> -#define WSEH_OLD 4
>> +#define WSEH_NEW (1<<12)
>> +#define WSEH_CONTEXT (1<<13)
>> +#define WSEH_OLD (1<<14)
>
> Hopefully this is a safe conversion, as everything should come from
> parse_ws_error_highlight() that uses these constants.
I reviewed the conversion again and I think it is safe, still.
We could do the up and downshifting for the flags to keep these
as-is, but I am not sure if that is a good idea, the up and downshifting
is not just run time complexity but also a readability issue.
>
> But this is brittle; there must be some hint to future readers of
> this code why these bits begin at 12th (it is linked to 07777 we saw
> earlier); otherwise when they change something that needs to widen
> that 07777, they will forget to shift these up, which would screw
> up everything that is carefully laid out here.
I added a note there. and a BUG check at the beginning of the output.
Smart compilers will drop that and for dumb compilers we'll have an
extra check per commit, which is not too bad
