Handle I/O errors gracefully on push.

If connection to upstream is hosed, consider nothing to have been
pushed.

fix glandium#338

src/main.rs

@@ -4845,25 +4845,28 @@ fn remote_helper_push(
                 let response = conn.unbundle(heads, file);
                 match response {
                     UnbundleResponse::Bundlev2(data) => {
-                        let mut bundle = BundleReader::new(data).unwrap();
-                        while let Some(part) = bundle.next_part().unwrap() {
-                            match part.part_type.as_bytes() {
-                                b"reply:changegroup" => {
-                                    // TODO: should check in-reply-to param.
-                                    let response = part.get_param("return").unwrap();
-                                    result = u32::from_str(response).ok();
-                                }
-                                b"error:abort" => {
-                                    let mut message =
-                                        part.get_param("message").unwrap().to_string();
-                                    if let Some(hint) = part.get_param("hint") {
-                                        message.push_str("\n\n");
-                                        message.push_str(hint);
+                        if let Ok(mut bundle) = BundleReader::new(data) {
+                            while let Ok(Some(part)) = bundle.next_part() {
+                                match part.part_type.as_bytes() {
+                                    b"reply:changegroup" => {
+                                        // TODO: should check in-reply-to param.
+                                        let response = part.get_param("return").unwrap();
+                                        result = u32::from_str(response).ok();
+                                    }
+                                    b"error:abort" => {
+                                        let mut message =
+                                            part.get_param("message").unwrap().to_string();
+                                        if let Some(hint) = part.get_param("hint") {
+                                            message.push_str("\n\n");
+                                            message.push_str(hint);
+                                        }
+                                        error!(target: "root", "{}", message);
                                     }
-                                    error!(target: "root", "{}", message);
+                                    _ => {}
                                 }
-                                _ => {}
                             }
+                        } else {
+                            pushed = ChangesetHeads::new();
                         }
                     }
                     UnbundleResponse::Raw(response) => {

tests/push.t

@@ -576,8 +576,6 @@ https://github.com/glandium/git-cinnabar/issues/341
 
 Verify that pushes to the divergent clone are rejected by a broken
 hook:
-XXX This should not crash git-cinnabar:
-https://github.com/glandium/git-cinnabar/issues/338
 
   $ cat <<EOF >repo/.hg/hgrc
   > [hooks]
@@ -591,9 +589,8 @@ https://github.com/glandium/git-cinnabar/issues/338
   remote: transaction abort!
   remote: rollback completed
   remote: abort: No such file or directory: '/nonexistent'
-  fatal: called `Result::unwrap()` on an `Err` value: Error { kind: UnexpectedEof, message: "failed to fill whole buffer" }
-  Run the command again with `git -c cinnabar.check=traceback <command>` to see the full traceback.
-  error: git-remote-hg died of signal 6
+  To hg::.*/push.t/repo (re)
+   ! [remote rejected] 846552c6f25c1b46e784f59d8249fb31afac2996 -> branches/default/tip (nothing changed on remote)
   error: failed to push some refs to 'hg::.*/push.t/repo' (re)
   [1]
   $ rm repo/.hg/hgrc