Cron – Tracking Crontab Changes with Git

See the Content Limitations section of the git Wiki: git does not track file ownership, group membership, doesn't track most permission bits, ACLs, access and modification times, etc.

Git tracks contents, and doesn't care much about pretty much everything else.

All users' crontabs are stored in a single directory, and users can't access that directory directly, they need to use the privileged command crontab.

Instead of storing the actual crontab file in version control, write a commit hook that runs crontab to push the latest version.

crontab "$HOSTNAME.crontab"

The simplest hook would be a post-commit hook. Run git rev-parse --abbrev-ref HEAD to find the current branch and git show --format=format: --name-status HEAD.

#!/bin/sh
commit=$(git rev-parse HEAD)
branch=$(git rev-parse --name-status "$commit")
git show --format=format: --name-status "$commit" |
while read -r status filename; do
  if [ "$branch" = "master" ] &&
     [ "$status" = "A" -o "$status" = "M" ] &&
     [ "$filename" = "crontabs/$HOSTNAME.crontab" ]; then
    crontab "$filename"
  fi
done

This doesn't handle merges or rebases, and doesn't register anything in the history if crontab fails. There's a bit of a paradigm clash here since git fundamentally has multiple branches but there's only a single crontab on a given machine at any given time. For added robustness, you might prefer to have a dedicated branch for live crontabs, and merge to that branch when you change the crontab file on your working branch.