- Select notification email by walking up group/subgroup path
- Add settings UI to set group email notification address
- Add tests

Extract diff line data attributes to helper methods

This reverts commit 13e37a3e.

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

Based on:
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/151

The repository push email can be very expensive to generate, especially
with syntax-highlighted diffs. Instead of generating the email for each
recipient, generate one email object and reset the Message-Id and To
headers for each recipient. (Cloning would also be expensive in the case
of large emails, although probably not as bad as generating from
scratch.)

Fixes #2098