To build and install:

% cd /usr/src/sbin
% git clone git@github.com:KlaraSystems/jectl.git jectl
% cd jectl
% make && make install

To see usage:
% jectl

See overview-jectl.txt for tool usage. This needs to be converted
into a manual page.

overview-zfs-layout.txt gives a brief explanation of how jectl
manipulates zfs datasets.

overview-generate-je.txt explains how to create jail environments
using poudriere-image(8) and generate-je.sh. The created jail
environments are meant to be consumed by jectl.