DumpConfig's lines that set nothing start with #, and a line starting with # runs as nothing at an exec, a ctl or the init file

DumpConfig's information lines ("Platform: tty", "Startup config: ...")
began with words. Written back, as the report means to be, or clicked,
each ran as a shell command or failed as an unknown control message.
Each now starts with `# `. A line starting with `#` is a comment, as in a
shell: it runs as nothing, silently, at an exec, at the root's, a pane's
or a column's ctl, and in the init file. Documented in fs.md and
config.md.

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

2 files changed, 21 insertions, 3 deletions

diff --git a/src/ninep/cols.zig b/src/ninep/cols.zig
index f07c7f39..24fb590c 100644
--- a/src/ninep/cols.zig
+++ b/src/ninep/cols.zig
@@ -163,7 +163,7 @@ pub fn writeCtl(p: *Pardes, req: Req, serial: u32) Reply {
     var lines = std.mem.splitScalar(u8, req.data, '\n');
     while (lines.next()) |raw| {
         const line = std.mem.trim(u8, raw, " \t\r");
-        if (line.len == 0) continue;
+        if (line.len == 0 or pardes.exec.isComment(line)) continue;
         const word = line[0 .. std.mem.indexOfAny(u8, line, " \t") orelse line.len];
         const takes = for ([_][]const u8{ "Delcol", "Joincol", "New", "Tty" }) |w| {
             if (std.mem.eql(u8, w, word)) break true;
diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index f4e6bb9c..cf0b241c 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -608,7 +608,7 @@ pub fn writeRoot(p: *Pardes, req: Req) Reply {
         if (apply) p.fs.results_len = 0;
         var it = Messages.init(p, req.data);
         while (it.next()) |line| {
-            if (line.len == 0) continue;
+            if (line.len == 0 or exec_line.isComment(line)) continue;
             if (std.mem.startsWith(u8, line, "size ") or std.mem.eql(u8, line, "size")) {
                 const size = sizeOf(line) orelse return refuse(p, req, e_size, line);
                 // A frontend's window is the size; only a session none is
@@ -834,7 +834,7 @@ pub fn writePane(p: *Pardes, req: Req, pane: *Pane) Reply {
         var held = !other and pane.fs.lock != null;
         var it = Messages.init(p, req.data);
         while (it.next()) |line_in| {
-            if (line_in.len == 0) continue;
+            if (line_in.len == 0 or exec_line.isComment(line_in)) continue;
             // A line before this one may have closed the pane (`Del`).
             if (apply and p.paneBySerial(serial) == null) return Reply.fail(req.tag, E.NOENT);
             // acme's ctl words: done by the file that replaces each, or the
@@ -2504,6 +2504,24 @@ test "with no pane at all, the root look opens its file and the root exec runs i
     try testing.expectEqualStrings(session, made.cwdSlice());
 }
 
+test "a line starting with # runs as nothing at an exec or a ctl, silently" {
+    const p = try withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    const serial = serialOf(p);
+    // The setup's own announcements are made by the first write's update.
+    _ = wr(p, @intFromEnum(tree.TopFile.ctl), "# settle\n");
+    const before = p.next_serial;
+    const log_before = try pardes.ctlfs.events.freezeLog(p);
+    defer p.gpa.free(log_before.bytes);
+    for ([_]u64{ @intFromEnum(tree.TopFile.exec), Node.of(serial, .exec), @intFromEnum(tree.TopFile.ctl), Node.of(serial, .ctl), Node.ofCol(layout.columnSerial(p, 0), .ctl) }) |node| {
+        try testing.expectEqual(Status.ok, wr(p, node, "# Platform: tty\n  # indented too\n").reply.status);
+    }
+    try testing.expectEqual(before, p.next_serial);
+    const log_after = try pardes.ctlfs.events.freezeLog(p);
+    defer p.gpa.free(log_after.bytes);
+    try testing.expectEqualStrings(log_before.bytes, log_after.bytes);
+}
+
 test "the ctl word name refuses a leading blank, as the name file does" {
     const p = try withFile(testing.allocator, "x\n");
     defer p.deinit();