Have JIRA send mails to watchers on commit from Stash on a ticket

In general the work flow you use requires Git Integration Plugin for JIRA or JIRA DVCS Connector (if you are using Bitbucket or Github) so I assume you use that.

An alternative is to use the JIRA REST API to handle your tickets with git hooks - this should trigger the notifications on the JIRA tickets, since it's basically a shortcut that handles your JIRA tickets directly from commit messages - it's same as if you did it manually.

Assuming you have Git Integration Plugin for Jira, to make your notifications work you will have to edit the Notification Scheme - you will have to setup the project permissions - specifically View Development Tools permission must be granted to Users > Group > Project Roles (read Setting Up Repositories on http://bigbrassband.com/documentation.html) in order to view the git related data on JIRA ticket.

You may also want to go through all settings in the plugin "Advanced setup" and check if any of this features is set to Disabled and enable it.

It looks like there's something called the Notification Assistant for JIRA. I'm pretty sure this is what my company uses to notify us of Github commits via the Hipchat application. Looks like there's a way to have it auto-generate emails for you too.

Take a look in the slideshow for it. Here's a couple screenshots that make me think this is what you're looking for.

Looking at the events within JIRA that can be notified from, other than "Generic Event" which I'm not sure when will be fired, perhaps using some of the other smart commit tags could help achieve this goal?

For example, developers could prepend their commit messages with ISSUE_KEY #comment so their commit comment gets added as a comment to the JIRA issue. Then you could configure the "Issue Commented" event to notify the appropriate people.