rust-update: handle SIGINT from long-running update threads The current code does not respond to ^C until after the Rust bit is finished doing its work. This is expected, since Rust holds the GIL for the duration of the call and does not call `PyErr_CheckSignals`. Freeing the GIL to do our work does not really improve anything since the Rust threads are still going, and the only way of cancelling a thread is by making it cooperate. So we do the following: - remember the SIGINT handler in hg-cpython and reset it after the call into core (see inline comment in `update.rs` about this) - make all update threads watch for a global `AtomicBool` being `true`, and if so stop their work - reset the global bool and exit early (i.e. before writing the dirstate) - raise SIGINT from `hg-cpython` if update returns `InterruptReceived`

--- a/rust/hg-core/src/errors.rs	Fri Nov 08 17:08:11 2024 +0100
+++ b/rust/hg-core/src/errors.rs	Tue Nov 12 12:52:13 2024 +0100
@@ -52,6 +52,8 @@
     RaceDetected(String),
     /// An invalid path was found
     Path(HgPathError),
+    /// An interrupt was received and we need to stop whatever we're doing
+    InterruptReceived,
 }
 
 /// Details about where an I/O error happened
@@ -121,6 +123,7 @@
                 write!(f, "encountered a race condition {context}")
             }
             HgError::Path(hg_path_error) => write!(f, "{}", hg_path_error),
+            HgError::InterruptReceived => write!(f, "interrupt received"),
         }
     }
 }