Merge "Force use of scp rather than sftp when possible"

git_review/cmd.py

@@ -373,9 +373,17 @@ def set_hooks_commit_msg(remote, target_file):
                 userhost = hostname
             # OS independent target file
             scp_target_file = target_file.replace(os.sep, "/")
+
+            # Get scp options
+            scp_out = run_command("scp")
+            scp_opts = scp_out[scp_out.index("[") + 2:scp_out.index("]")]
+
             cmd = ["scp", userhost + ":hooks/commit-msg", scp_target_file]
             if port is not None:
                 cmd.insert(1, "-P%s" % port)
+            # Force scp protocol if the -O option is available
+            if "O" in scp_opts:
+                cmd.insert(1, "-O")
 
             if VERBOSE:
                 hook_url = 'scp://%s%s/hooks/commit-msg' \

releasenotes/notes/scp-subsystem-c8d78aa8f7f69f66.yaml

@@ -0,0 +1,15 @@
+---
+fixes:
+  - |
+    OpenSSH has deprecated its use of scp/rcp protocol in favor of
+    SFTP, which the embedded Apache mina-sshd in widely-deployed
+    Gerrit versions does not yet support. The default officially
+    changed in OpenSSH 9.0 (some distributions, such as Fedora and
+    CentOS, switched their default behavior to this as early as
+    OpenSSH 8.7 or 8.8), leading to a ``subsystem request failed on
+    channel 0`` error during commit-msg hook retrieval. Now
+    git-review will attempt to detect whether scp's -O option is
+    available to force use of the legacy scp/rcp protocol, and apply
+    it if so. Future git-review versions may change the fallback
+    behavior once an SFTP subsystem is implemented and available for
+    a new Gerrit release.