Magic Variable - Change the name of the variable to assign the local variable for partial, rather than `i` use the `index`.

Don't pass a local variable called `i` to a partial.

When destroying a namespace, the `skip_repo` parameter is supposed
to prevent the repository directory from being destroyed and allow
the namespace after_destroy hook to run. If the namespace fails
to be deleted for some reason, we could be left with repositories
that are deleted with existing projects.

The helper constructs the path for a given oauth provider since Devise 4.0 deprecated passing the provider to the omniauth authentication path.

Fixes #18110.

So we have raw_diffs too

This object will manage Gitlab::Git::Compare instances

Instead calling diff_collection.count use diff_collection.size which is cache on the diff_collection

Introducing the concept of SafeDiffs which relates 
diffs with UI highlighting.

Speedup DiffNote#active? on discussions, preloading noteables and avoid touching git repository to return diff_refs when possible

- Preloading noteable we share the same noteable instance when more than one 
discussion refers to the same noteable.
- Any other call to that object that is cached in that object will be for any 
discussion.
- In those cases where merge_request_diff has all the sha stored to build a diff_refs get that 
diff_refs using directly those sha instead accessing to the git repository to first get the 
commits and later the sha.

This reverts commit 1bba46d6.

Now we link to the standard `IssuesController#new` action, and let it
redirect if we're using an external tracker.

Prior, in order to display the correct link to "Issues" in the project
navigation, we were performing a check against the project to see if it
used an external issue tracker, and if so, we used that URL. This was
inefficient.

Now, we simply _always_ link to `namespace_project_issues_path`, and
then in the controller we redirect to the external tracker if it's
present.

This also removes the need for the url_for_issue helper. Bonus! 🎉

Provide more sensible default sort order for issues and merge requests
based on the following table:

| type           | state  | default sort order |
|----------------|--------|--------------------|
| issues         | open   | last created       |
| issues         | closed | last updated       |
| issues         | all    | last created       |
| merge requests | open   | last created       |
| merge requests | merged | last updated       |
| merge requests | closed | last updated       |
| merge requests | all    | last created       |

squashed - fixed label and milestone association problems, updated specs and refactored reader class a bit

When importing a pull request from GitHub, the old and new branches may
no longer actually exist by those names, but we need to recreate the
merge request diff with the right source and target shas.

We use these `target_branch_sha` and `source_branch_sha` attributes to
force these to the intended values. But the reader methods were always
looking up to the target/source branch head instead of check if these
values was previously set.