Add cron instructions

README.md

@@ -60,17 +60,32 @@ First create a new blank project. Do not import a project. Choose 'git' in the
 like https://git.overleaf.com/5efb2cbe8306d30001f4cba8.
 
 ```shell script
+git clone git@gitlab.astro-wise.org:buddel/gitremotesync.git
 git clone git@gitlab.astro-wise.org:buddel/testlatex2.git
 cd testlatex2
 git remote rename origin gitlab
+git config credential.helper store
 git remote add overleaf https://git.overleaf.com/5efb2cbe8306d30001f4cba8
 git fetch overleaf
-git merge -X ours overleaf/master
+git merge -X ours overleaf/master --allow-unrelated-histories
 git push overleaf master
 git push gitlab master
 ```
 
+The overleaf default main tex file is `main.tex`. You should remove that file
+if the imported gitlab project uses a different main tex file.
+
 ### Setup from existing Overleaf repository
 This is simpler, just create an empty project on GitLab (that is, do not
 initialize with a readme), clone the Overleaf repository like usual, add
 the GitLab remote and push there.
+
+### Setup cron
+
+The synchronization can be automated by a cronjob. E.g. to synchronize every
+5 minutes:
+```shell_script
+(crontab -l ; echo "*/5 * * * * cd $(pwd) && bash ../gitremotesync/synchronize.sh") | crontab -
+```
+The synchronization scripts only outputs something when changes are propagated,
+so cron will only send an email when synchronization has occurred.