Make export blocks default to json on stdout (#5090)

* Make export blocks default to json on stdout

* Multiline instead of single line to stay under 100 cols

* Change --json flag to --binary, defaulting to json

substrate/client/service/src/builder.rs

@@ -742,7 +742,7 @@ pub trait ServiceBuilderCommand {
 		output: impl Write + 'static,
 		from: NumberFor<Self::Block>,
 		to: Option<NumberFor<Self::Block>>,
-		json: bool
+		binary: bool
 	) -> Pin<Box<dyn Future<Output = Result<(), Error>>>>;
 
 	/// Performs a revert of `blocks` blocks.

substrate/client/service/src/chain_ops.rs

@@ -203,7 +203,7 @@ impl<
 		mut output: impl Write + 'static,
 		from: NumberFor<TBl>,
 		to: Option<NumberFor<TBl>>,
-		json: bool
+		binary: bool
 	) -> Pin<Box<dyn Future<Output = Result<(), Error>>>> {
 		let client = self.client;
 		let mut block = from;
@@ -230,7 +230,7 @@ impl<
 
 			if !wrote_header {
 				info!("Exporting blocks from #{} to #{}", block, last);
-				if !json {
+				if binary {
 					let last_: u64 = last.saturated_into::<u64>();
 					let block_: u64 = block.saturated_into::<u64>();
 					let len: u64 = last_ - block_ + 1;
@@ -241,13 +241,13 @@ impl<
 
 			match client.block(&BlockId::number(block))? {
 				Some(block) => {
-					if json {
+					if binary {
+						output.write_all(&block.encode())?;
+					} else {
 						serde_json::to_writer(&mut output, &block)
 							.map_err(|e| format!("Error writing JSON: {}", e))?;
-						} else {
-							output.write_all(&block.encode())?;
 					}
-				},
+			},
 				// Reached end of the chain.
 				None => return std::task::Poll::Ready(Ok(())),
 			}