Add character diff highlighting in emails on push service

• Zendesk ticket: https://gitlab.zendesk.com/agent/tickets/10126
• Dev link: None
• GitLab version: 8.0

Email on push service does not have character-level diff highlighting. Customer requests that we add this capability so diff highlighting is in line with the web view.

Web diff view with character-level highlighting

Email on push current diff example

Next steps

Is this possible? What amount of work is necessary?

cc/ @DouweM

Right now diff highlighting in the UI and in the Emails on Push email are done using a very different method. Using the method used in the UI in Emails on Push is not hard though, since we can just reuse most of the code.

I estimate this can be done in an hour.

Thanks @DouweM

@JobV Can we schedule this for a future release, please?

@JobV Please schedule this for a future release when you have time.

Milestone changed to 8.5

Milestone changed to 8.4

Hey guys, I noticed there is a bug with diff highlighting so you might want to fix that first, see #3451 (closed).

Added diff ~15897 highlight labels

This is made much easier by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2109. Once that is in, I will work on this.

Reassigned to @DouweM

mentioned in issue #12821 (closed)

@DouweM If you're looking at this one, there is an add-on request from the same company. See gitlab-org/gitlab-ce#12821. If it all makes sense to do it together, please do. Otherwise, we can treat it separately.

@dblessing already addressed by https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/151 which mostly unifies web diffs and email diffs :)

@DouweM Awesome! Thanks for your work on this.

Milestone changed to 8.6

Status changed to closed by commit gitlab-org/gitlab-ee@2fd9ae8b7fe5f24ba8e22f6b3c53a3ef4b15baf2

mentioned in issue #17464 (closed)

Mentioned in commit pfjason/gitlab-ce@2fd9ae8b

mentioned in merge request !14785