NOTIFY_EMAIL

#!/bin/sh

branch=$(echo "$1" | sed 's#refs/[^/]*/##')
repo="$GL_REPO/$branch"
mail_subject="$repo changed by $GL_USER"
oldcommit="$2"
if test "$2" = 0000000000000000000000000000000000000000; then
    # New branch
    oldcommit="$(git rev-parse --not --all | grep -v "$3" | git rev-list --stdin "$3" | tail -n 1)^"
fi
mail_text=$(git log "${oldcommit}..$3" --decorate --graph)

subscribers=$(git show $3:.subscribers 2>/dev/null)

for mail_to in $subscribers; do
    echo "$mail_text" | mail -s "$mail_subject" -c '' "$mail_to" &
done

To activate, add

repo    @all
  -     VREF/NOTIFY_EMAIL          = @all

in the gitolite.conf.