Support commenting on a diff in side-by-side view
### What does this MR do?
This MR adds support for commenting on a diff in side-by-side (aka parallel) view. It also fixes a JavaScript bug (see !779) when the comment button is clicked on a line that already has a comment.
There is an existing bug where the comment count is not updated when a new comment is added. I'll send a MR for that later.
### Why was this MR needed?
Commenting only worked in "inline" mode. Often the side-by-side view is more conducive to writing comments.
### What are the relevant issue numbers?
Closes https://github.com/gitlabhq/gitlabhq/issues/9283
### Screenshot

See merge request !810
Fix hooks for web based events with external issue references
The creation of cross references for external issues (which would fail)
is now prevented. This fixes a 500 error and the execution of hooks when
creating a merge request or commenting on one.
Fixes#1650, GH-9333.
This regression might have been introduced by
8f8a8ab32b. There is actually a TODO by
@rspeicher mentioning external issues which is lost (unhandled) in a
later commit.
This fix is related to !766 and !804 which fix a similar issue for hooks for
Git based events.
See merge request !794
Prepare blog post in advance
Prepare the blog posts template directly after merging the old one. This way people can add add items that should not be forgotten during the month.
See merge request !816
Fix external issue tracker hook/test for HTTPS URLs
If HTTPS was used for the 'project_url' of an external issue tracker, an
error was raised because a HTTP connection was established to the
default HTTPS port.
The code has been corrected and simplified by using HTTParty.
Additionally, the request now is made directly to the 'project_url'
instead of the extracted root path.
## The bug is reproducible on gitlab.com
1. Set up a new external issue service (I used Redmine)
2. Set the project URL to 'http://example.com/redmine/projects/x' and
click on 'Test settings' => Ok
3. Now set the URL to 'https://example.com/redmine/projects/x' and test
it again => 500
## What is actually happening?
Web servers behave differently when a non-SSL connection is established
to a SSL port:
- Nginx / Apache 2.4: Status code 400
- Apache 2.2: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">...
(no status code line is sent)
- example.com: Empty response, no status code line
## Relevant log entries
```
2015-06-04T11:10:47.972Z 16785 TID-exfks WARN: {"retry"=>true, "queue"=>"project_web_hook", "class"=>"ProjectServiceWorker", "args"=>[...], "error_message"=>"wrong status line: \"<!DOCTYPE HTML PUBLIC \\\"-//IETF//DTD HTML 2.0//EN\\\">\"", "error_class"=>"Net::HTTPBadResponse", ...}
2015-06-04T11:10:47.972Z 16785 TID-exfks WARN: wrong status line: "<!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">"
2015-06-04T11:10:47.972Z 16785 TID-exfks WARN: /usr/lib/ruby/2.1.0/net/http/response.rb:41:in `read_status_line'
[...]
/home/git/gitlab-7.11.4/app/models/project_services/issue_tracker_service.rb:88:in `execute'
/home/git/gitlab-7.11.4/app/workers/project_service_worker.rb:8:in `perform'
[...]
```
See merge request !767