[bug-diffutils] bug#20062: bug#20062: bug#20062: bug#20062: bug#20062: bug#20062: [PATCH] diff: add support for --color

[Jim Meyering]

Thank you for that patch and for your patience.
I've skimmed through and so far have only a question and a request:

Regarding this section:

+void
+set_header_color_context (void)
+{
+  process_signals ();
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[1;39m");
+}
+
+void
+set_line_numbers_color_context (void)
+{
+  process_signals ();
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[36m");
+}
+
+void
+set_add_color_context (void)
+{
+  process_signals ();
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[32m");
+  fflush (outfile);
+}
+
+void
+set_delete_color_context (void)
+{
+  process_signals ();
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[31m");
+}
+
+void
+reset_color_context (void)
+{
+  static char const reset_sequence[] = "\x1b[0m";
+  if (! colors_enabled)
+    return;
+
+  fputs (reset_sequence, outfile);
+}

Why does set_add_color_context call fflush, yet the others do not?
Please use fputs rather than fprintf for those literal strings.
The former is often far more efficient.

Finally, should there be some way to specify different colors,
e.g., for those who use different-background-colored terminals,
or for the color blind?