Merge branch 'jk/fallthrough'

Many codepaths have been updated to squelch -Wimplicit-fallthrough
warnings from Gcc 7 (which is a good code hygiene).

* jk/fallthrough:
  consistently use "fallthrough" comments in switches
  curl_trace(): eliminate switch fallthrough
  test-line-buffer: simplify command parsing

read-cache.c

@@ -220,6 +220,7 @@ static int ce_modified_check_fs(const struct cache_entry *ce, struct stat *st)
 	case S_IFDIR:
 		if (S_ISGITLINK(ce->ce_mode))
 			return ce_compare_gitlink(ce) ? DATA_CHANGED : 0;
+		/* else fallthrough */
 	default:
 		return TYPE_CHANGED;
 	}