Be able to email commit authors

Have something like $AUTHORS which will email all who submitted since last pull in case of error.

Emails of all authors of un-pulled remote changes:

git --no-pager log --pretty='%ae' HEAD..@{u} | sort | uniq

Consider the case where there is no existing repository and authors are all authors.

git --no-pager log --pretty='%ae' | sort | uniq

For specific branch add "--branches=test".

And the payload seems to contain info about the pusher.