Merge branch 'zj/diff-empty-chmod'

"git diff --stat" used to fully count a binary file with modified
execution bits whose contents is unmodified, which was not right.

By Zbigniew Jędrzejewski-Szmek (4) and Johannes Sixt (1)
* zj/diff-empty-chmod:
t4006: Windows do not have /dev/zero
diff --stat: do not run diff on indentical files
diff --stat: report mode-only changes for binary files like text files
tests: check --[short]stat output after chmod
test: modernize style of t4006

Conflicts:
diff.c

diff --combined diff.c
index 02081d2af249d7fef660bd401a6d508b2e21cff1,8e61f4bf857eb80ec067336604fba2382eb4219c..77edd5086fff30af36e92a151377c285de21aca3
--- 1/diff.c
--- 2/diff.c
+++ b/diff.c
@@@ -1443,8 -1443,8 +1443,8 @@@ static void show_stats(struct diffstat_
  {
        int i, len, add, del, adds = 0, dels = 0;
        uintmax_t max_change = 0, max_len = 0;
 -      int total_files = data->nr;
 -      int width, name_width, graph_width, number_width = 4, count;
 +      int total_files = data->nr, count;
 +      int width, name_width, graph_width, number_width = 0, bin_width = 0;
        const char *reset, *add_c, *del_c;
        const char *line_prefix = "";
        int extra_shown = 0;
@@@ -1480,21 -1480,8 +1480,21 @@@
                if (max_len < len)
                        max_len = len;
  
 -              if (file->is_binary || file->is_unmerged)
 +              if (file->is_unmerged) {
 +                      /* "Unmerged" is 8 characters */
 +                      bin_width = bin_width < 8 ? 8 : bin_width;
                        continue;
 +              }
 +              if (file->is_binary) {
 +                      /* "Bin XXX -> YYY bytes" */
 +                      int w = 14 + decimal_width(file->added)
 +                              + decimal_width(file->deleted);
 +                      bin_width = bin_width < w ? w : bin_width;
 +                      /* Display change counts aligned with "Bin" */
 +                      number_width = 3;
 +                      continue;
 +              }
 +
                if (max_change < change)
                        max_change = change;
        }
@@@ -1519,22 -1506,12 +1519,22 @@@
         * stat_name_width fixes the maximum width of the filename,
         * and is also used to divide available columns if there
         * aren't enough.
 +       *
 +       * Binary files are displayed with "Bin XXX -> YYY bytes"
 +       * instead of the change count and graph. This part is treated
 +       * similarly to the graph part, except that it is not
 +       * "scaled". If total width is too small to accomodate the
 +       * guaranteed minimum width of the filename part and the
 +       * separators and this message, this message will "overflow"
 +       * making the line longer than the maximum width.
         */
  
        if (options->stat_width == -1)
 -              width = term_columns();
 +              width = term_columns() - options->output_prefix_length;
        else
                width = options->stat_width ? options->stat_width : 80;
 +      number_width = decimal_width(max_change) > number_width ?
 +              decimal_width(max_change) : number_width;
  
        if (options->stat_graph_width == -1)
                options->stat_graph_width = diff_stat_graph_width;
@@@ -1548,14 -1525,10 +1548,14 @@@
  
        /*
         * First assign sizes that are wanted, ignoring available width.
 +       * strlen("Bin XXX -> YYY bytes") == bin_width, and the part
 +       * starting from "XXX" should fit in graph_width.
         */
 -      graph_width = (options->stat_graph_width &&
 -                     options->stat_graph_width < max_change) ?
 -              options->stat_graph_width : max_change;
 +      graph_width = max_change + 4 > bin_width ? max_change : bin_width - 4;
 +      if (options->stat_graph_width &&
 +          options->stat_graph_width < graph_width)
 +              graph_width = options->stat_graph_width;
 +
        name_width = (options->stat_name_width > 0 &&
                      options->stat_name_width < max_len) ?
                options->stat_name_width : max_len;
@@@ -1564,12 -1537,8 +1564,12 @@@
         * Adjust adjustable widths not to exceed maximum width
         */
        if (name_width + number_width + 6 + graph_width > width) {
 -              if (graph_width > width * 3/8 - number_width - 6)
 +              if (graph_width > width * 3/8 - number_width - 6) {
                        graph_width = width * 3/8 - number_width - 6;
 +                      if (graph_width < 6)
 +                              graph_width = 6;
 +              }
 +
                if (options->stat_graph_width &&
                    graph_width > options->stat_graph_width)
                        graph_width = options->stat_graph_width;
@@@ -1614,8 -1583,12 +1614,12 @@@
                if (data->files[i]->is_binary) {
                        fprintf(options->file, "%s", line_prefix);
                        show_name(options->file, prefix, name, len);
-                       fprintf(options->file, " %*s ", number_width, "Bin");
-                       fprintf(options->file, "%s%"PRIuMAX"%s",
 -                      fprintf(options->file, "  Bin");
++                      fprintf(options->file, " %*s", number_width, "Bin");
+                       if (!added && !deleted) {
+                               putc('\n', options->file);
+                               continue;
+                       }
+                       fprintf(options->file, " %s%"PRIuMAX"%s",
                                del_c, deleted, reset);
                        fprintf(options->file, " -> ");
                        fprintf(options->file, "%s%"PRIuMAX"%s",
@@@ -1627,7 -1600,7 +1631,7 @@@
                else if (data->files[i]->is_unmerged) {
                        fprintf(options->file, "%s", line_prefix);
                        show_name(options->file, prefix, name, len);
 -                      fprintf(options->file, "  Unmerged\n");
 +                      fprintf(options->file, " Unmerged\n");
                        continue;
                }
  
@@@ -1656,9 -1629,8 +1660,9 @@@
                }
                fprintf(options->file, "%s", line_prefix);
                show_name(options->file, prefix, name, len);
 -              fprintf(options->file, "%5"PRIuMAX"%s", added + deleted,
 -                              added + deleted ? " " : "");
 +              fprintf(options->file, " %*"PRIuMAX"%s",
 +                      number_width, added + deleted,
 +                      added + deleted ? " " : "");
                show_graph(options->file, '+', add, add_c, reset);
                show_graph(options->file, '-', del, del_c, reset);
                fprintf(options->file, "\n");
@@@ -1689,17 -1661,16 +1693,16 @@@ static void show_shortstats(struct diff
                return;
  
        for (i = 0; i < data->nr; i++) {
-               if (!data->files[i]->is_binary &&
-                   !data->files[i]->is_unmerged) {
-                       int added = data->files[i]->added;
-                       int deleted= data->files[i]->deleted;
-                       if (!data->files[i]->is_renamed &&
-                           (added + deleted == 0)) {
-                               total_files--;
-                       } else {
-                               adds += added;
-                               dels += deleted;
-                       }
+               int added = data->files[i]->added;
+               int deleted= data->files[i]->deleted;
+ 
+               if (data->files[i]->is_unmerged)
+                       continue;
+               if (!data->files[i]->is_renamed && (added + deleted == 0)) {
+                       total_files--;
+               } else {
+                       adds += added;
+                       dels += deleted;
                }
        }
        if (options->output_prefix) {
@@@ -2399,6 -2370,7 +2402,7 @@@ static void builtin_diffstat(const cha
  {
        mmfile_t mf1, mf2;
        struct diffstat_file *data;
+       int same_contents;
  
        data = diffstat_add(diffstat, name_a, name_b);
  
@@@ -2407,10 -2379,17 +2411,17 @@@
                return;
        }
  
+       same_contents = !hashcmp(one->sha1, two->sha1);
+ 
        if (diff_filespec_is_binary(one) || diff_filespec_is_binary(two)) {
                data->is_binary = 1;
-               data->added = diff_filespec_size(two);
-               data->deleted = diff_filespec_size(one);
+               if (same_contents) {
+                       data->added = 0;
+                       data->deleted = 0;
+               } else {
+                       data->added = diff_filespec_size(two);
+                       data->deleted = diff_filespec_size(one);
+               }
        }
  
        else if (complete_rewrite) {
@@@ -2420,7 -2399,7 +2431,7 @@@
                data->added = count_lines(two->data, two->size);
        }
  
-       else {
+       else if (!same_contents) {
                /* Crazy xdl interfaces.. */
                xpparam_t xpp;
                xdemitconf_t xecfg;