Record /log whether or not anyone reads it, with the editor's messages in it

/log is now one ring (64 KiB, 4 KiB on the board) that records new, del,
rename and save, and a msg line for everything the editor says. An open
freezes it, so cat log shows what happened lately and ends; writing
follow to that same open makes reads past it wait for newer records, and
a follower the ring outran reads lost N first.

The message log keeps the pane's serial, not its reusable slot.

A test now fails when the tree serves a file /README never mentions; it
caught pty/status, now documented along with typing through pty/data.

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

2 files changed, 18 insertions, 7 deletions

diff --git a/test/fs.py b/test/fs.py
index 33bcdfa9..48104e3f 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -185,7 +185,11 @@ def discovery(binary, embedded=False):
             # An open of /pane/new makes a pane and the read names it; each
             # open makes another. A stat makes none, which is why new can be
             # listed at all: ls -l stats every name a listing gave it.
-            log = client.open('/log')
+            # /log answers the recent past and ends; `follow` written to the
+            # same open makes its reads past that wait for new records.
+            log = client.open('/log', 2)
+            frozen = len(client.read_fid(log))
+            client.rpc(118, struct.pack('<IQI', log, 0, 7) + b'follow\n')
             first = int(client.read('/pane/new'))
             assert first == newest(client)
             second = int(client.read('/pane/new'))
@@ -193,8 +197,14 @@ def discovery(binary, embedded=False):
             assert 'new' in client.list('/pane'), 'new should be visible to ls'
             client.stat('/pane/new')
             assert newest(client) == second, 'a stat of new made a pane'
-            assert client.read_fid(log) == f'new {first} {root}/+New\n'.encode()
-            assert client.read_fid(log) == f'new {second} {root}/+New\n'.encode()
+            # What the editor said is in the stream too, and the fixture's own
+            # `new` lands on whichever side of the open its first update did.
+            def pane_event():
+                while (record := client.read_fid(log, frozen)).startswith((b'msg ', f'new {fixture} '.encode())):
+                    pass
+                return record
+            assert pane_event() == f'new {first} {root}/+New\n'.encode()
+            assert pane_event() == f'new {second} {root}/+New\n'.encode()
             assert set(client.list('/pane')) == {'new', str(fixture), str(first), str(second)}
             client.write(f'/pane/{first}/body', b'first pane', truncate=True)
             assert client.read(f'/pane/{first}/body') == b'first pane'
@@ -206,7 +216,7 @@ def discovery(binary, embedded=False):
             assert client.read(f'/pane/{first}/name') == f'{root}/+New\n'.encode()
             client.write(f'/pane/{first}/name', b'notes.txt\n')
             assert client.read(f'/pane/{first}/name') == f'{root}/notes.txt\n'.encode()
-            assert client.read_fid(log) == f'rename {first} {root}/notes.txt\n'.encode()
+            assert pane_event() == f'rename {first} {root}/notes.txt\n'.encode()
             assert client.stat(f'/pane/{first}/name')['length'] == len(f'{root}/notes.txt\n')
             # Copying addr onto dot selects that range; sel reads and replaces it.
             client.write(f'/pane/{first}/addr', b'#0,#5')
@@ -223,11 +233,11 @@ def discovery(binary, embedded=False):
             assert client.read(f'/pane/{first}/dirty') == b'1\n'
             client.write(f'/pane/{first}/exec', b'Save\n')
             assert (root / 'notes.txt').read_bytes() == b'FIRST pane'
-            assert client.read_fid(log) == f'save {first} {root}/notes.txt\n'.encode()
+            assert pane_event() == f'save {first} {root}/notes.txt\n'.encode()
             assert client.read('/exec') == f'{first}\n'.encode()
             assert client.read(f'/pane/{first}/dirty') == b'0\n'
             client.remove(f'/pane/{second}')
-            assert client.read_fid(log) == f'del {second} {root}/+New\n'.encode()
+            assert pane_event() == f'del {second} {root}/+New\n'.encode()
             assert str(second) not in client.list('/pane')
             # look opens a file; the serial reads back.
             (root / 'opened.txt').write_bytes(b'one\ntwo\nthree\n')
@@ -236,7 +246,7 @@ def discovery(binary, embedded=False):
             assert opened not in (fixture, first, second), opened
             assert client.read(f'/pane/{opened}/body') == b'one\ntwo\nthree\n'
             assert client.read(f'/pane/{opened}/name') == f'{root}/opened.txt\n'.encode()
-            assert client.read_fid(log) == f'new {opened} {root}/opened.txt\n'.encode()
+            assert pane_event() == f'new {opened} {root}/opened.txt\n'.encode()
             client.write(f'/pane/{first}/look', f'{root}/opened.txt:3\n'.encode())
             assert client.read('/look') == f'{opened}\n'.encode(), 'a repeated look targets the open pane'
             assert {str(fixture), str(first), str(opened)} <= set(client.list('/pane'))
diff --git a/test/panes.zig b/test/panes.zig
index 2d3aed43..2f307cb5 100644
--- a/test/panes.zig
+++ b/test/panes.zig
@@ -2193,6 +2193,7 @@ test "document panes ignore terminal output without allocating terminal state" {
     const p = try Pardes.init(allocator.allocator(), .{ .tty_only = true });
     defer p.deinit();
     const pane = try p.setTestFile("document body\n");
+    p.update(.tick); // the step that installed it records it in /log
     while (p.nextEffect()) |_| {}
     const revision = pane.file.?.revision;
     const allocations = allocator.alloc_index;