enhance: kill superseded history queries when refreshing commits

src/Commands/Command.cs

@@ -229,6 +229,19 @@ protected ProcessStartInfo CreateGitStartInfo(bool redirect)
             return start;
         }
 
+        protected CancellationTokenRegistration TerminateOnCancellation(Process proc)
+        {
+            if (!CancellationToken.CanBeCanceled)
+                return default;
+
+            // Disposing the returned registration waits for a running callback, so `proc` is always valid inside it.
+            return CancellationToken.Register(() =>
+            {
+                if (!proc.HasExited)
+                    Native.OS.TerminateProcess(proc);
+            });
+        }
+
         protected void RaiseException(string error)
         {
             Models.Notification.Send(Context, error, true);

src/Commands/QueryCommits.cs

@@ -59,6 +59,8 @@ public QueryCommits(string repo, string filter, Models.CommitSearchMethod method
                 proc.StartInfo = CreateGitStartInfo(true);
                 proc.Start();
 
+                using var cancellation = TerminateOnCancellation(proc);
+
                 var findHead = false;
                 while (await proc.StandardOutput.ReadLineAsync().ConfigureAwait(false) is { } line)
                 {
@@ -82,9 +84,13 @@ public QueryCommits(string repo, string filter, Models.CommitSearchMethod method
 
                 await proc.WaitForExitAsync().ConfigureAwait(false);
 
+                if (CancellationToken.IsCancellationRequested)
+                    return commits;
+
                 if (_markMerged && !findHead && commits.Count > 0)
                 {
                     var set = await new QueryCurrentBranchCommitHashes(WorkingDirectory, commits[^1].CommitterTime)
+                        .WithCancellation(CancellationToken)
                         .GetResultAsync()
                         .ConfigureAwait(false);
 
@@ -100,7 +106,8 @@ public QueryCommits(string repo, string filter, Models.CommitSearchMethod method
             }
             catch (Exception e)
             {
-                RaiseException($"Failed to query commits. Reason: {e.Message}");
+                if (!CancellationToken.IsCancellationRequested)
+                    RaiseException($"Failed to query commits. Reason: {e.Message}");
             }
 
             return commits;

src/Commands/QueryCurrentBranchCommitHashes.cs

@@ -23,6 +23,8 @@ public async Task<HashSet<string>> GetResultAsync()
                 proc.StartInfo = CreateGitStartInfo(true);
                 proc.Start();
 
+                using var cancellation = TerminateOnCancellation(proc);
+
                 while (await proc.StandardOutput.ReadLineAsync().ConfigureAwait(false) is { Length: > 8 } line)
                     outs.Add(line);
 

src/ViewModels/Repository.cs

@@ -1276,6 +1276,7 @@ public void RefreshCommits()
                 }
 
                 var commits = await new Commands.QueryCommits(FullPath, builder.ToString())
+                    .WithCancellation(token)
                     .GetResultAsync()
                     .ConfigureAwait(false);