A builtin failure over something not there answers ENOENT: Unmount of a name not mounted

`Unmount nothere` failed EIO with `not mounted`. It says `no such mount
nothere` now, and a builtin's failure that says `no such` (this, Tty's
`no such directory`) answers ENOENT, the errno 9ns reads from those words.

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

1 files changed, 8 insertions, 1 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index 59fc140d..095eadbd 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -705,7 +705,14 @@ pub const Unmount = struct {
         var args = std.mem.tokenizeAny(u8, c.arg orelse "", " \t");
         const name = args.next() orelse return c.p.reportError(c.id, "Unmount name", error.MissingArgument);
         if (args.next() != null) return c.p.reportError(c.id, "Unmount name", error.TooManyArguments);
-        pardes.filesystem.unmount(c.p, name) catch |err| return c.p.reportError(c.id, "Unmount", err);
+        pardes.filesystem.unmount(c.p, name) catch |err| {
+            // "no such": the words 9ns reads as ENOENT.
+            if (err == error.NotMounted) {
+                var said: [96]u8 = undefined;
+                return c.p.reportFailure(c.id, std.fmt.bufPrint(&said, "Unmount: no such mount {s}", .{name[0..@min(name.len, 32)]}) catch "Unmount: no such mount");
+            }
+            return c.p.reportError(c.id, "Unmount", err);
+        };
     }
 };