fix: assure we flush before turning a writer into a reader. (#1061)

Otherwise it might be that the write-end still isn't flushed, so
the receiver didn't get the message it's waiting on, which wouild
cause us to deadlock while waiting for a response from the remote.

Author: Byron

gix-transport/src/client/async_io/request.rs

@@ -83,7 +83,9 @@ impl<'a> RequestWriter<'a> {
     ///
     /// Doing so will also write the message type this instance was initialized with.
     pub async fn into_read(mut self) -> std::io::Result<Box<dyn ExtendedBufRead + Unpin + 'a>> {
+        use futures_lite::AsyncWriteExt;
         self.write_message(self.on_into_read).await?;
+        self.writer.inner_mut().flush().await?;
         Ok(self.reader)
     }
 

gix-transport/src/client/blocking_io/request.rs

@@ -1,4 +1,5 @@
 use std::io;
+use std::io::Write;
 
 use crate::client::{ExtendedBufRead, MessageKind, WriteMode};
 
@@ -60,6 +61,7 @@ impl<'a> RequestWriter<'a> {
     /// Doing so will also write the message type this instance was initialized with.
     pub fn into_read(mut self) -> std::io::Result<Box<dyn ExtendedBufRead + Unpin + 'a>> {
         self.write_message(self.on_into_read)?;
+        self.writer.inner_mut().flush()?;
         Ok(self.reader)
     }