fix(justfile): test-sixel-tmux skips nesting when already inside tmux

Running `just test-sixel-tmux' from a tmux pane previously printed
`sessions should be nested with care, unset $TMUX to force' and exited
with code 1.  Switch the recipe to a shebang body that branches at
runtime: when `$TMUX' is already set, run emacs directly in the
current pane (the test condition is already satisfied -- we're inside
tmux); otherwise spawn a fresh `tmux new-session' wrapper as before.

1 files changed, 21 insertions, 8 deletions

diff --git a/justfile b/justfile
index 008f4ad..306290e 100644
--- a/justfile
+++ b/justfile
@@ -145,15 +145,28 @@ test-sixel-image encoder="":
         --eval "(kitty-graphics-mode 1)" \
         tests/test-image.png
 
-# Open test-image.png inside `tmux new-session', sixel backend forced
-# (run on a sixel-capable outer terminal, requires tmux >= 3.4)
+# Open test-image.png inside tmux with sixel backend forced.
+# Outer terminal must be sixel-capable (foot, Konsole, mintty, mlterm, WezTerm).
+# Requires tmux >= 3.4 built with --enable-sixel.
+# When already inside tmux, runs emacs directly (no nesting).
 test-sixel-tmux encoder="":
-    @echo ">> Outer terminal must be sixel-capable (foot, Konsole, mintty, ...)."
-    @echo ">> tmux >= 3.4 with --enable-sixel required."
-    tmux new-session -As kgfx-sixel-test "TERM={{TERM_}} {{EMACS}} -nw -Q -l {{SRC}} \
-        --eval '(setq kitty-gfx-debug t kitty-gfx-preferred-protocol (quote sixel))' \
-        --eval '(when (> (length \"{{encoder}}\") 0) (setq kitty-gfx-sixel-encoder-program \"{{encoder}}\"))' \
-        --eval '(kitty-graphics-mode 1)' tests/test-image.png"
+    #!/usr/bin/env bash
+    set -eu
+    if [ -n "${TMUX:-}" ]; then
+        echo ">> Already inside tmux -- running emacs directly in this pane."
+        exec env TERM={{TERM_}} {{EMACS}} -nw -Q -l {{SRC}} \
+            --eval '(setq kitty-gfx-debug t kitty-gfx-preferred-protocol (quote sixel))' \
+            --eval '(when (> (length "{{encoder}}") 0) (setq kitty-gfx-sixel-encoder-program "{{encoder}}"))' \
+            --eval '(kitty-graphics-mode 1)' \
+            tests/test-image.png
+    else
+        echo ">> Outer terminal must be sixel-capable; spawning fresh tmux session."
+        exec tmux new-session -As kgfx-sixel-test \
+            "TERM={{TERM_}} {{EMACS}} -nw -Q -l {{SRC}} \
+                --eval '(setq kitty-gfx-debug t kitty-gfx-preferred-protocol (quote sixel))' \
+                --eval '(when (> (length \"{{encoder}}\") 0) (setq kitty-gfx-sixel-encoder-program \"{{encoder}}\"))' \
+                --eval '(kitty-graphics-mode 1)' tests/test-image.png"
+    fi
 
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