And another test.

regress/if-shell-nested.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+# 882
+# tmux inside if-shell itself should work
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -Ltest"
+$TMUX kill-server 2>/dev/null
+
+TMP=$(mktemp)
+trap "rm -f $TMP" 0 1 15
+
+cat <<EOF >$TMP
+if '$TMUX run "true"' 'set -s @done yes'
+EOF
+
+TERM=xterm $TMUX -f$TMP new -d "$TMUX show -vs @done >>$TMP" || exit 1
+sleep 1 && [ "$(tail -1 $TMP)" = "yes" ] || exit 1
+
+$TMUX has 2>/dev/null && exit 1
+
+exit 0