pkt-line: define PACKET_READ_RESPONSE_END

In a future commit, we will use PACKET_READ_RESPONSE_END to separate
messages proxied by remote-curl. To prepare for this, add the
PACKET_READ_RESPONSE_END enum value.

In switch statements that need a case added, die() or BUG() when a
PACKET_READ_RESPONSE_END is unexpected. Otherwise, mirror how
PACKET_READ_DELIM is implemented (especially in cases where packets are
being forwarded).

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

connect.c

@@ -127,6 +127,7 @@ enum protocol_version discover_version(struct packet_reader *reader)
 		die_initial_contact(0);
 	case PACKET_READ_FLUSH:
 	case PACKET_READ_DELIM:
+	case PACKET_READ_RESPONSE_END:
 		version = protocol_v0;
 		break;
 	case PACKET_READ_NORMAL:
@@ -310,6 +311,7 @@ struct ref **get_remote_heads(struct packet_reader *reader,
 			state = EXPECTING_DONE;
 			break;
 		case PACKET_READ_DELIM:
+		case PACKET_READ_RESPONSE_END:
 			die(_("invalid packet"));
 		}
 

pkt-line.c

@@ -99,6 +99,13 @@ void packet_delim(int fd)
 		die_errno(_("unable to write delim packet"));
 }
 
+void packet_response_end(int fd)
+{
+	packet_trace("0002", 4, 1);
+	if (write_in_full(fd, "0002", 4) < 0)
+		die_errno(_("unable to write stateless separator packet"));
+}
+
 int packet_flush_gently(int fd)
 {
 	packet_trace("0000", 4, 1);
@@ -337,6 +344,10 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 		packet_trace("0001", 4, 0);
 		*pktlen = 0;
 		return PACKET_READ_DELIM;
+	} else if (len == 2) {
+		packet_trace("0002", 4, 0);
+		*pktlen = 0;
+		return PACKET_READ_RESPONSE_END;
 	} else if (len < 4) {
 		die(_("protocol error: bad line length %d"), len);
 	}

pkt-line.h

@@ -22,6 +22,7 @@
  */
 void packet_flush(int fd);
 void packet_delim(int fd);
+void packet_response_end(int fd);
 void packet_write_fmt(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
 void packet_buf_flush(struct strbuf *buf);
 void packet_buf_delim(struct strbuf *buf);
@@ -94,6 +95,7 @@ enum packet_read_status {
 	PACKET_READ_NORMAL,
 	PACKET_READ_FLUSH,
 	PACKET_READ_DELIM,
+	PACKET_READ_RESPONSE_END,
 };
 enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 						size_t *src_len, char *buffer,

remote-curl.c

@@ -601,6 +601,8 @@ static int rpc_read_from_out(struct rpc_state *rpc, int options,
 		case PACKET_READ_FLUSH:
 			memcpy(buf - 4, "0000", 4);
 			break;
+		case PACKET_READ_RESPONSE_END:
+			die(_("remote server sent stateless separator"));
 		}
 	}
 

serve.c

@@ -217,6 +217,8 @@ static int process_request(void)
 
 			state = PROCESS_REQUEST_DONE;
 			break;
+		case PACKET_READ_RESPONSE_END:
+			BUG("unexpected stateless separator packet");
 		}
 	}
 

t/helper/test-pkt-line.c

@@ -46,6 +46,9 @@ static void unpack(void)
 		case PACKET_READ_DELIM:
 			printf("0001\n");
 			break;
+		case PACKET_READ_RESPONSE_END:
+			printf("0002\n");
+			break;
 		}
 	}
 }
@@ -75,6 +78,7 @@ static void unpack_sideband(void)
 		case PACKET_READ_FLUSH:
 			return;
 		case PACKET_READ_DELIM:
+		case PACKET_READ_RESPONSE_END:
 			break;
 		}
 	}