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]>

1 files changed, 37 insertions, 9 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index aca8d109..f98429ab 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -117,8 +117,8 @@ pub const TopFile = enum(u4) {
     pub fn mode(f: TopFile) u16 {
         return switch (f) {
             .root, .pane => 0o755,
-            .look, .exec => 0o666,
-            .README, .index, .status, .log, .screen, .listeners, .new => 0o444,
+            .look, .exec, .log => 0o666,
+            .README, .index, .status, .screen, .listeners, .new => 0o444,
         };
     }
 
@@ -375,7 +375,7 @@ fn topSize(p: *Pardes, f: TopFile) u64 {
         .README => fs.help.len,
         .status => ctl.statusLen(p),
         .look, .exec => ctl.resultsLen(p),
-        .log => events.pending(&p.fs.log),
+        .log => events.logLen(&p.fs.log),
         .listeners => screen.listenersLen(p),
     };
 }
@@ -497,7 +497,7 @@ fn open(p: *Pardes, req: Req, target: Target) Reply {
         .top => |f| switch (f) {
             .new => return .{ .tag = req.tag, .handle = makePane(p) orelse return Reply.fail(req.tag, E.NFILE) },
             .screen => return screen.openSnapshot(p, req, true),
-            .log => p.fs.log_readers +|= 1,
+            .log => return events.openLog(p, req),
             else => {},
         },
         .pane => |t| {
@@ -543,10 +543,7 @@ fn releaseHandle(p: *Pardes, req: Req) Reply {
     if (screen.releaseSnapshot(p, req)) return .{ .tag = req.tag };
     const target = Node.target(req.node) orelse return .{ .tag = req.tag };
     switch (target) {
-        .top => |f| if (f == .log and p.fs.log_readers > 0) {
-            p.fs.log_readers -= 1;
-            if (p.fs.log_readers == 0) p.fs.log.clearAndFree(p.gpa);
-        },
+        .top => {},
         .pane => |t| {
             if (t.file != .event and t.file != .pty_data) return .{ .tag = req.tag };
             const id = p.paneBySerial(t.serial) orelse return .{ .tag = req.tag };
@@ -597,7 +594,7 @@ fn read(p: *Pardes, req: Req, target: Target) Reply {
             },
             .status => ctl.readStatus(p, req),
             .look, .exec => ctl.readResults(p, req),
-            .log => events.readQueue(p, req, &p.fs.log),
+            .log => events.readLog(p, req),
             .screen => screen.readSnapshot(p, req, null),
             .listeners => screen.readListeners(p, req),
             // The serial the open handed this fid, so that two reads of one
@@ -623,6 +620,7 @@ fn write(p: *Pardes, req: Req, target: Target) Reply {
     switch (target) {
         .top => |f| return switch (f) {
             .look, .exec => ctl.command(p, req, null, f == .exec),
+            .log => events.writeLog(p, req),
             else => Reply.fail(req.tag, E.PERM),
         },
         .pane => |t| {
@@ -730,6 +728,36 @@ test "filesystem pane creation and truncation cancel Look hover" {
     }
 }
 
+test "README names every file the tree serves" {
+    // /README is the whole manual a client gets; a file it never mentions
+    // is one nobody can find without reading this source.
+    const words = struct {
+        fn has(name: []const u8) bool {
+            var it = std.mem.tokenizeAny(u8, fs.help, " \t\n,.:;()'\"$<>|=/");
+            while (it.next()) |w| if (std.mem.eql(u8, w, name)) return true;
+            return false;
+        }
+    };
+    inline for (@typeInfo(TopFile).@"enum".fields) |f| {
+        const t: TopFile = @enumFromInt(f.value);
+        if (t != .root and !words.has(t.fileName())) {
+            std.debug.print("README does not mention /{s}\n", .{t.fileName()});
+            return error.Undocumented;
+        }
+    }
+    inline for (@typeInfo(PaneFile).@"enum".fields) |f| {
+        const t: PaneFile = @enumFromInt(f.value);
+        const ok = if (t == .dir) true else if (t.inPty() and t != .pty)
+            std.mem.indexOf(u8, fs.help, "pty/" ++ comptime @as(PaneFile, @enumFromInt(f.value)).fileName()) != null
+        else
+            words.has(t.fileName());
+        if (!ok) {
+            std.debug.print("README does not mention pane file {s}\n", .{@tagName(t)});
+            return error.Undocumented;
+        }
+    }
+}
+
 test "readdir lists the root and a pane directory without creating anything" {
     const gpa = testing.allocator;
     const p = try withFile(gpa, "hello\n");