add pre start command

README.md

@@ -14,6 +14,7 @@ Here is an example for my 1337 Telegram Bot. The Timer "calls" a script which se
 ```
 timers:
    1337TelegramBot:
+      timer_precommand: /bin/bash -c '! /usr/bin/systemctl is-active --quiet other-service.service'
       timer_command: /home/telegrambot/sendMessage.pl
       timer_user: telegrambot
       timer_OnCalendar: "*-*-* 13:37:00 CET"
@@ -26,6 +27,7 @@ That's all the magic.
 
 | Variable | Required |  Default value / Explanation |
 |----------|----------|------------------------------|
+| timer_precommand | no | Pre-command before command |
 | timer_command |  yes | Which command or script to execute |
 | timer_user | no | Under which users the timer_command is executed. Default: root |
 | timer_persistent | no | Takes a boolean argument. If true, the time when the service unit was last triggered is stored on disk. When the timer is activated, the service unit is triggered immediately if it would have been triggered at least once during the time when the timer was inactive. This is useful to catch up on missed runs of the service when the machine was off. Note that this setting only has an effect on timers configured with OnCalendar=. Defaults to false. [Source](https://www.freedesktop.org/software/systemd/man/systemd.timer.html) |

templates/service.j2

@@ -7,6 +7,9 @@ Description={{ item.key }} Service
 
 [Service]
 Type=oneshot
+{% if item.value.timer_precommand is defined %}
+ExecStartPre={{ item.value.timer_precommand }} 
+{% endif %}
 ExecStart={{ item.value.timer_command }}
 {% if item.value.timer_user is defined %}
 User={{ item.value.timer_user }}