tests: add testshell.sh and port old testsuite.txt

Add a simple helper script testshell.sh that can be called
to set up an environment for generating test case transcripts
that can then be pasted into an actual test script.

Port old testsuite.txt into t9999-testsuite_example.sh
with the aim of refactoring it later into smaller tests.

Also, change test_todo_session to count from one instead of zero when
autogenerating tests.

Signed-off-by: Emil Sit <sit@emilsit.net>

tests/test-lib.sh

@@ -471,7 +471,7 @@ test_tick () {
 test_todo_session () {
     test "$#" = 1 ||
     error "bug in the test script: extra args to test_todo_session"
-    subnum=0
+    subnum=1
     cmd=""
     status=0
     > expect
@@ -513,6 +513,18 @@ test_todo_session () {
     fi
 }
 
+test_shell () {
+	trap - EXIT
+	export PS1='$(ret_val=$?; [ "$ret_val" != "0" ] && echo -e "=== $ret_val\n\n>>> "||echo "\n>>> ")'
+	cat <<EOF
+Do your tests session here and
+don't forget to replace the hardcoded path with \$HOME in the transcript:
+$HOME/todo.txt => \$HOME/todo.txt
+EOF
+	bash --noprofile --norc
+	exit 0
+}
+
 test_init_todo "$test"
 # Use -P to resolve symlinks in our working directory so that the cwd
 # in subprocesses equals our $PWD (for pathname comparisons).