Tests: Add basic coverage of -h / shorthelp.

For a start, this is basically an adapted version of tests/t2100-help.sh.

tests/t2120-shorthelp.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+#
+
+test_description='shorthelp functionality
+
+This test covers the output of the -h option and the shorthelp action.
+'
+. ./actions-test-lib.sh
+. ./test-lib.sh
+
+# Note: To avoid having to adapt the test whenever the actions change, only
+# check for the section headers.
+test_todo_session '-h output' <<EOF
+>>> todo.sh -h | sed '/^  [A-Z]/!d'
+  Usage: todo.sh [-fhpantvV] [-d todo_config] action [task_number] [task_description]
+  Actions:
+  Actions can be added and overridden using scripts in the actions
+  See "help" for more details.
+EOF
+
+test_todo_session 'shorthelp output' <<EOF
+>>> todo.sh shorthelp | sed '/^  [A-Z]/!d'
+  Usage: todo.sh [-fhpantvV] [-d todo_config] action [task_number] [task_description]
+  Actions:
+  Actions can be added and overridden using scripts in the actions
+  See "help" for more details.
+EOF
+
+make_action "foo"
+test_todo_session 'shorthelp output with custom action' <<EOF
+>>> todo.sh -v shorthelp | sed '/^  [A-Z]/!d'
+  Usage: todo.sh [-fhpantvV] [-d todo_config] action [task_number] [task_description]
+  Actions:
+  Actions can be added and overridden using scripts in the actions
+  Add-on Actions:
+  See "help" for more details.
+EOF
+
+test_done