Plain text emails lack content of HTML emails

Copied from https://github.com/gitlabhq/gitlabhq/issues/9434

Let's say a new issue is created on my project. I get an email which contains:

message/rfc822 multipart/alternative text/plain text/html

The text/html part contains the actual contents of the new issue, but the text/plain part only gives me the very basic, e.g. that a new issue was created, who the author was, and the link to the gitlab.com issue.

Please include at least the contents of the initial bug report in the text/plain part. Ideally it should be functionally similar to the text/html part. This also shouldn't be limited to just new issue emails.