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.

On a merge request with over 1000 changed files, there were redundant
calls to blob_text_viewable?, which incurred about 7% of the time.

Improves #14775

We can't reuse the existing value of the format parameter, because on
the merge request page that's 'json', so the link would go to a JSON
file. We can't set it to HTML, because that adds '.html' the URL, which
breaks the compare view (and looks bad). Setting it to nil uses the
default format, which in all of these cases is HTML anyway.

Other diffs (those that are too large to render anyway, image diffs,
diffs suppressed by .gitattributes) should be rendered immediately.

With the option to expand and collapse individual diffs, these aren't
needed any more.

When rendering a list of diff files, skip those where the diff is over
10 KB and provide an endpoint to render individually instead.

Extract parts of LegacyDiffNote into DiffOnNote concern and move part of responsibility to other classes

Extract diff line data attributes to helper methods

This reverts commit 13e37a3e.

Here was the problem:

1. When determining whether a given blob is viewable text, gitlab_git reads the first 1024 bytes and checks with Linguist whether it is a text or binary file.
2. If the blob is text, GitLab will attempt to display it.
3. However, if the text has binary characters after the first 1024 bytes, then GitLab will attempt to load the entire contents, but the encoding will be ASCII-8BIT since there are binary characters.
4. The Error 500 results when GitLab attempts to display a mix UTF-8 and ASCII-8BIT.

To fix this, we load as much data as we are willing to display so that the detection will work properly. Requires
an update to gitlab_git: gitlab-org/gitlab_git!86

Closes #13826

added whitespace toggle to diffs page and set it to return the project compare path with the selected whitespace params

Updated CHANGELOG

Moved CHANGELOG entry

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

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

This is a combination of 3 commits.

- Update the bare repositories info/attributes if the default branch is updated
- Check the diff attributes of a file before showing a diff
- Update CHANGELOG