A terminal's Tty word names its shell, Tty+fish, and a click on it opens another

A terminal's tag said Tty whatever shell it ran. The host's acknowledgement
of the shell it forked now sets the word to Tty+<shell>, tinted like the tag's
name. Word+arg is taken as Word arg, one word a tag can hold and a click can
take whole (+ is a word character), so Tty+fish opens a terminal on fish, as
Tty fish does; Tty takes the shell as its argument, which the host forks for
that pane instead of the configured one. Every snapshot whose screen shows a
terminal's tag changes: 69 goldens, re-recorded by name, whose 297 changed
lines are all Tty becoming Tty+bash (the harness runs bash), the cursor
columns and style spans that moved with it, or that text cut at a pane's
width.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index 19d16e1e..02787cf5 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -818,9 +818,16 @@ pub const DelBelow = struct {
 
 /// A shell in the calling pane's directory, raw from the first frame. On every
 /// pane's tagline: the fast path from wherever you are to a prompt there.
+/// A terminal below the caller in its directory: the configured shell, or
+/// the one named, `Tty fish`, as a terminal's own tag word `Tty+fish` says.
 pub const Tty = struct {
+    pub const takes_arg = true;
     pub fn run(c: Ctx) void {
         exec.spawnTty(c.p, c.id);
+        const arg = c.arg orelse return;
+        const pane = c.p.panes[c.p.active] orelse return;
+        if (!pane.isTerminal() or pane.shell != null) return;
+        pane.shell = c.p.gpa.dupe(u8, arg) catch return;
     }
 };