runcron.sh

#!/bin/sh

# Copyright 2023 Codeberg e.V.
# This work is marked with CC0 1.0 Universal. To view a copy of this
# license, visit http://creativecommons.org/publicdomain/zero/1.0
# This work is dedicated to the public domains under the terms of the
# Unlicense, visit https://unlicense.org/
# You are free to choose either the CC0 1.0 Univesal or Unlicense for this
# work.

# via https://mastodon.social/@Codeberg@social.anoxinon.de/111524635192557943

repo=""  # url to repository
dir=""   # directory to cd into (or fail)
refspec="main"

cd $dir || exit 2
if [ -d repo.git ]; then
        cd repo.git
	OLD_HEAD=$(git rev-parse HEAD)
	git pull -q origin $refspec
	NEW_HEAD=$(git rev-parse HEAD)
else
	git clone -q "$repo" repo.git
        cd repo.git
	OLD_HEAD=xxx
	NEW_HEAD=$(git rev-parse HEAD)
fi

[ $OLD_HEAD = $NEW_HEAD ] && exit

# now perform whatever you want to do ...

echo "I am in $(pwd)"