Merge branch 'ep/maint-equals-null-cocci'

Introduce and apply coccinelle rule to discourage an explicit
comparison between a pointer and NULL, and applies the clean-up to
the maintenance track.

* ep/maint-equals-null-cocci:
  tree-wide: apply equals-null.cocci
  tree-wide: apply equals-null.cocci
  contrib/coccinnelle: add equals-null.cocci

builtin/rev-parse.c

@@ -476,7 +476,7 @@ static int cmd_parseopt(int argc, const char **argv, const char *prefix)
 
 		/* name(s) */
 		s = strpbrk(sb.buf, flag_chars);
-		if (s == NULL)
+		if (!s)
 			s = help;
 
 		if (s - sb.buf == 1) /* short option only */