Split off dedicated tests for listpri.

Bonus: Fixed alignment of listpri help message.

tests/t1250-listpri.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+
+test_description='list priority functionality
+'
+. ./test-lib.sh
+
+test_todo_session 'listpri usage' <<EOF
+>>> todo.sh listpri ?
+usage: todo.sh listpri PRIORITY
+note: PRIORITY must a single letter from A to Z.
+=== 1
+EOF
+
+cat > todo.txt <<EOF
+(B) smell the uppercase Roses +flowers @outside
+(C) notice the sunflowers
+stop
+EOF
+test_todo_session 'basic listpri' <<EOF
+>>> todo.sh listpri A
+--
+TODO: 0 of 3 tasks shown
+
+>>> todo.sh -p listpri c
+2 (C) notice the sunflowers
+--
+TODO: 1 of 3 tasks shown
+EOF
+test_done