test: Add testenv_enter.sh to ease debugging testenv

The script testenv_enter.sh, by default, runs /bin/sh in the environment
currently setup.

A bit easier than copy pasting the old hint text printed before test run.

Signed-off-by: Magnus Malm <magnusmalm@gmail.com>

test/testenv_enter.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+set -eu
+
+cmd=""
+if [ "$#" -lt 1 ]; then
+    cmd="/bin/sh"
+else
+    cmd=$1
+    shift
+fi
+
+PID_FILE=$(dirname "$0")/running_test.pid
+
+if [ -f  "$PID_FILE" ] ; then
+    target=$(cat "$PID_FILE")
+    target=$(pgrep -P "$target")
+else
+    echo "No test running!"
+    exit 1
+fi
+
+"$(dirname "$0")"/testenv_exec.sh "$target" "$cmd" "$@"