Refactoring: Extract make_action into actions-test-lib.sh.

This reduces the duplication in the individual test files.

tests/t2100-help.sh

@@ -5,10 +5,9 @@ test_description='help functionality
 
 This test covers the help output.
 '
+. ./actions-test-lib.sh
 . ./test-lib.sh
 
-unset TODO_ACTIONS_DIR
-
 # Note: To avoid having to adapt the test whenever the help documentation
 # slightly changes, only check for the section headers.
 test_todo_session 'help output' <<EOF
@@ -33,16 +32,6 @@ test_todo_session 'very verbose help output' <<EOF
   Built-in Actions:
 EOF
 
-mkdir .todo.actions.d
-make_action()
-{
-	cat > ".todo.actions.d/$1" <<- EOF
-	#!/bin/bash
-	echo "custom action $1"
-EOF
-chmod +x ".todo.actions.d/$1"
-}
-
 make_action "foo"
 test_todo_session 'help output with custom action' <<EOF
 >>> todo.sh -v help | sed '/^  \w/!d'