Use 3 as the minimum width of formatted line numbers

It gives a more pleasant experience when "digging" through commits.
And of course, most commits will have diffs smaller than 1000 lines!?
For the blame view it means less flickering in the startup when the
whole file is read.

tig.c

@@ -1490,14 +1490,15 @@ draw_lineno(struct view *view, unsigned int lineno, int max, bool selected)
 {
 	static char fmt[] = "%1ld";
 	char number[10] = "          ";
-	int max_number = MIN(view->digits, STRING_SIZE(number));
+	int digits3 = view->digits < 3 ? 3 : view->digits;
+	int max_number = MIN(digits3, STRING_SIZE(number));
 	bool showtrimmed = FALSE;
 	int col;
 
 	lineno += view->offset + 1;
 	if (lineno == 1 || (lineno % opt_num_interval) == 0) {
 		if (view->digits <= 9)
-			fmt[1] = '0' + view->digits;
+			fmt[1] = '0' + digits3;
 
 		if (!string_format(number, fmt, lineno))
 			number[0] = 0;