Enhancement: Stream JSON output for ls command The `ls` command now supports JSON output with the global `--json` flag, and this change streams out JSON messages one object at a time rather than en entire array buffered in memory before encoding. The advantage is it allows large listings to be handled efficiently. Two message types are printed: snapshots and nodes. A snapshot object will precede node objects which belong to that snapshot. The `struct_type` field can be used to determine which kind of message an object is. https://github.com/restic/restic/pull/1962