Edit's refusals name the pattern, not the line, and say when dot is empty

A ctl Edit that missed answered `Edit: no match for regexp "Edit
/nomatch/d"`, quoting the whole program; it now names the address that
missed (`no match for regexp /nomatch/`) and quotes no line after. An s
on an empty dot says `no substitution: dot is empty`. A \\1 is blamed
only once its pattern has matched, as before. tags.md says & is special
in s and not in c, a or i, as in sam.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index e1dd3fc5..2fdc47cc 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -332,7 +332,10 @@ pub fn runBuiltin(p: *Pardes, req: Req, id: usize, line: []const u8) ?Reply {
     if (!created) noteResult(p, context);
     if (p.fs.refused) return refuse(p, req, e_prompt, line);
     if (p.fs.failure_len == 0) return null;
-    const refusal = refuse(p, req, p.fs.failure[0..p.fs.failure_len], line);
+    // An Edit's failure names what failed (the pattern that missed): its
+    // line, a program, is not quoted after it.
+    const edit = std.mem.startsWith(u8, line, "Edit ") or std.mem.eql(u8, line, "Edit");
+    const refusal = if (edit) tree.failText(req.tag, E.IO, p.fs.failure[0..p.fs.failure_len]) else refuse(p, req, p.fs.failure[0..p.fs.failure_len], line);
     return .{ .tag = req.tag, .status = .err, .errno = E.IO, .ename = refusal.ename };
 }