Repl's unknown-language refusal names a few whole and points to the rest

The refusal listed every language and was clipped to fit, ending mid-word.
It now names six, those that start as the word did first (pithon:
python), says how many more, and points at docs/tags.md, which lists them
all.

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

1 files changed, 18 insertions, 3 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index 87a4d022..4490482d 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -1075,10 +1075,25 @@ pub const Repl = struct {
         // Named as a code fence names it: `py`, `Python`, `sh`.
         const named: ?u8 = if (manifest.byName(arg)) |i| if (grammars[i].exts.len > 0) @intCast(i) else null else null;
         const lang: u8 = named orelse {
+            // A few, whole, and where the rest are: a list cut to fit the
+            // row would end mid-word.
             var w = std.Io.Writer.fixed(&buf);
-            w.print("Repl: no language \"{s}\"; - or one of:", .{@import("Messages.zig").clip(arg, 24)}) catch {};
-            for (grammars) |g| if (g.exts.len > 0) w.print(" {s}", .{g.name}) catch break;
-            return c.p.reportFailure(c.id, @import("Messages.zig").clip(w.buffered(), 256));
+            w.print("Repl: no language \"{s}\"; - or one like", .{@import("Messages.zig").clip(arg, 24)}) catch {};
+            // Those that start as the word does first, a misspelling's
+            // likeliest meaning (pithon: python).
+            var shown: usize = 0;
+            var known: usize = 0;
+            for ([2]bool{ true, false }) |alike| for (grammars) |g| if (g.exts.len > 0) {
+                const starts = arg.len > 0 and g.name[0] == std.ascii.toLower(arg[0]);
+                if (starts != alike) continue;
+                known += 1;
+                if (shown < 6) {
+                    w.print(" {s}", .{g.name}) catch {};
+                    shown += 1;
+                }
+            };
+            w.print(" ({d} more: docs/tags.md, Repl)", .{known - shown}) catch {};
+            return c.p.reportFailure(c.id, w.buffered());
         };
         if (pane.repl) |r| if (r.lang == lang)
             return c.p.setMessage(c.id, std.fmt.bufPrint(&buf, "Repl: {s}", .{exec.replId(&idbuf, pane)}) catch "Repl");