Most of the fields allow you to specify a special tag (##tag##) which will
be replaced at hook execution. It is a feature that allows you to minimize
the number of hooks you must maintain.
The complete list of tags:
- ##repo## - the repository name
- ##branch## - the branch name just created or pushed to
- ##hook_id## - the id of the hook
- ##commit## - the git's SHA-1 commit id
- ##date## - the UTC date (example: 2016-01-15)
- ##time## - the UTC time (example: 00:36:23)
- ##timestamp## - the UNIX epoch (example: 1452810114)
- ##ip## - the IP address from where the push took place