[clone] Support explicitly closing (v2) connections

It's a no-op for everyone else or stateless transports like HTTP

git-transport/src/client/file.rs

@@ -121,6 +121,14 @@ impl client::Transport for SpawnProcessOnDemand {
             .request(write_mode, on_drop)
     }
 
+    fn close(mut self) -> Result<(), client::Error> {
+        if let Some(c) = self.connection.take() {
+            c.close()
+        } else {
+            Ok(())
+        }
+    }
+
     fn to_url(&self) -> String {
         self.url.to_string()
     }

git-transport/src/client/git.rs

@@ -118,6 +118,15 @@ where
             on_drop,
         ))
     }
+
+    fn close(mut self) -> Result<(), client::Error> {
+        if self.version == Protocol::V2 {
+            git_packetline::encode::flush_to_write(&mut self.writer)?;
+            self.writer.flush()?;
+        }
+        Ok(())
+    }
+
     fn to_url(&self) -> String {
         git_url::Url {
             scheme: git_url::Scheme::File,

git-transport/src/client/http/mod.rs

@@ -164,6 +164,11 @@ impl<H: Http> client::Transport for Transport<H> {
             on_drop,
         ))
     }
+
+    fn close(self) -> Result<(), client::Error> {
+        Ok(())
+    }
+
     fn to_url(&self) -> String {
         self.url.to_owned()
     }

git-transport/src/client/mod.rs

@@ -211,6 +211,9 @@ pub trait Transport {
     /// If `handle_progress` is not None, it's function passed a text line without trailing LF from which progress information can be parsed.
     fn request(&mut self, write_mode: WriteMode, on_drop: Vec<MessageKind>) -> Result<RequestWriter, Error>;
 
+    /// Closes the connection to indicate no further requests will be made.
+    fn close(self) -> Result<(), Error>;
+
     /// Returns the canonical URL pointing to the destination of this transport.
     /// Please note that local paths may not be represented correctly, as they will go through a potentially lossy
     /// unicode conversion.

git-transport/tests/client/git.rs

@@ -143,6 +143,8 @@ fn handshake_v1_and_request() -> crate::Result {
     drop(reader);
     let sidebands = Rc::try_unwrap(messages).expect("no other handle").into_inner();
     assert_eq!(sidebands.len(), 6, "…along with some status messages");
+    c.close()?;
+
     assert_eq!(
         out.as_slice().as_bstr(),
         b"002egit-upload-pack /foo.git\0host=example.org\0000ahello\n\
@@ -281,6 +283,7 @@ fn handshake_v2_and_request() -> crate::Result {
     drop(res);
     let messages = Rc::try_unwrap(messages).expect("no other handle").into_inner();
     assert_eq!(messages.len(), 4);
+    c.close()?;
 
     assert_eq!(
         out.as_slice().as_bstr(),
@@ -300,7 +303,7 @@ fn handshake_v2_and_request() -> crate::Result {
 000eofs-delta
 0032want 808e50d724f604f69ab93c6da2919c014667bedb
 0009done
-0000"
+00000000"
             .as_bstr(),
         "it sends the correct request, including the adjusted version"
     );

git-transport/tests/client/http/mod.rs

@@ -200,6 +200,8 @@ fn handshake_v1() -> crate::Result {
             "e8df6c1ffb7afa27aff9abbe11c7e4b80d19b61e refs/tags/v0.3.0^{}"
         ]
     );
+    c.close()?;
+
     assert_eq!(
         server.received_as_string().lines().collect::<Vec<_>>(),
         format!(
@@ -405,6 +407,7 @@ Accept: application/x-git-upload-pack-result
     drop(res);
     let messages = Rc::try_unwrap(messages).expect("no other handle").into_inner();
     assert_eq!(messages.len(), 5);
+    c.close()?;
 
     assert_eq!(
         server.received_as_string().lines().collect::<Vec<_>>(),