Git hooks allow you to process git metadata at various points in the commit cycle. Reference: https://git-scm.com/docs/githooks.
Configure a global git hooks directory
$ git config --global core.hookspath ~/lib/githooks/
Make the hooks executable and place them in the hooks directory.
This hook assumes you have feature branches with names that look like feature/PROJ-666.
Places you in the editor with a default commit message of the form
[PROJ-666] <you must have a one-line banner-type message here>
Creates a commit message of the form
[PROJ-666] msg
Creates a commit message of the form
[PROJ-666] one
two