Re: [PATCHv3 1/3] diff.c: omit hidden entries from namelen calculation with --stat

Michael J Gruber [off-list ref] writes:

Again, I'm sorry I'm not seeing through the call chain here.

diff_flush() notices it needs to produce textual patch and count added or
deleted lines here:

	if (output_format & (DIFF_FORMAT_DIFFSTAT|DIFF_FORMAT...
		struct diffstat_t diffstat;

		memset(&diffstat, 0, sizeof(struct diffstat_t));
		for (i = 0; i < q->nr; i++) {
			struct diff_filepair *p = q->queue[i];
			if (check_pair_status(p))
				diff_flush_stat(p, options, &diffstat);
		}
		if (output_format & DIFF_FORMAT_NUMSTAT)
			show_numstat(&diffstat, options);
		if (output_format & DIFF_FORMAT_DIFFSTAT)
			show_stats(&diffstat, options);
		if (output_format & DIFF_FORMAT_SHORTSTAT)
			show_shortstats(&diffstat, options);
		free_diffstat_info(&diffstat);
		separator++;
	}

In the loop, it calls diff_flush_stat() for each and every filepair in the
queue.  The result is collected in &diffstat, and that is what your patch
works on in show_stats() function.  Before you look at it in show_stats(),
the same &diffstat may be examined by show_numstat(), and after you look
at it, the same &diffstat may be examined by show_shortstats().

diff_flush_stat() calls run_diffstat() to get textual patch for one
filepair. It ends up calling builtin_diffstat().

builtin_diffstat() looks at the preimage and postimage, and feeds the low
level xdiff machinery with it, and uses diffstat_consume() callbac to
count the +/- lines in the patch between the two.

Even though three show_*stat* function look at the same &diffstat, two
have duplicated logic to ignore (and uncount) a path whose executable
bit was changed without any other change, with:

	if (!it->is_renamed && (added + deleted) == 0)
        	ignore it!