A failed builtin's err replaces its msg, and (xN) is a running total

A builtin failing a ctl write logged its Verbose announcement, its words as
a msg, and the write's err, so the same failure again never repeated the
newest record and never collapsed. Its err alone is logged now (the msg is
still shown and kept in +Messages). A repeat of a record a follower has
read is a new line with the running total, (xN) being N in all. fs.md
states both rules.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 76f09084..d1bb5907 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -1406,3 +1406,18 @@ test "Shell refuses a path that is no executable, and bare it goes back to the d
     var want: [300]u8 = undefined;
     try testing.expect(std.mem.indexOf(u8, rd(p, root_ctl, 0, 8192).bytes, try std.fmt.bufPrint(&want, "Shell {s}\n", .{config.defaultShell()})) != null);
 }
+
+test "a builtin that fails a ctl write logs only its err, so the same failure again is counted" {
+    const p = try withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    p.update(.tick); // the pane's `new` is logged first
+    while (p.nextEffect()) |_| {}
+    const ctl_node = @intFromEnum(tree.TopFile.ctl);
+    for (0..3) |_| try testing.expectEqual(Status.err, wr(p, ctl_node, "Kill zzz\n").reply.status);
+    const log = @intFromEnum(tree.TopFile.log);
+    const h = call(p, .{ .tag = 1, .op = .open, .node = log }).reply.handle;
+    const text = call(p, .{ .tag = 2, .op = .read, .node = log, .handle = h, .size = 1 << 16 }).bytes;
+    try testing.expect(std.mem.endsWith(u8, text, "err - ctl: Kill: no running command has that first word \"Kill zzz\" (x3)\n"));
+    try testing.expect(std.mem.indexOf(u8, text, "msg - Kill") == null);
+    _ = call(p, .{ .tag = 3, .op = .release, .node = log, .handle = h });
+}