If `current_signin_tab` is `#crowd`, then no tab will be active. Fix
this by using the first available tab.

Relates to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20049#note_82996324

This notifies developers when calling `find(_by!)` chained on
`execute`. And suggests using the methods from `FinderMethods`. These
will perform the correct authorization checks on the resource when it
is found.

There is still the edge case when 'no commits' changes to 'conflict'
would not trigger notification, which we ignore for now.

Calling can_be_merged? can cause exception (e.g. non-UTF8)
Ignore those by rescueing.

Remove unmergeable_reason as now only conflict is notified

Update spec

This reverts merge request !19873

The blue shortcut commit button opens the commit interface to
actually perform the commit. The ellipsis indicates the button doesn't
immediately perform the commit.

Since Rails 5.0 `request.format` is being set depending on the route extension.

In commits pages we pass a ref as a URL parameter.
If the ref is an extension-like, Rails converts it and sets to
`request.format`.

E.g. if the ref is `some_branch.atom`, Rails starts responding with
`atom` format, but it should response with `html` because `.atom` is the
part of ref name, not the format.

This commit explicitly sets `request.format` to `:html` when needed.

Rails5 fix  expected: 0 times with any arguments received: 1 time with arguments: DashboardController

Operations and Kubernetes items are now omitted in the sidebar when repository or builds are disabled

Closes https://gitlab.com/gitlab-org/gitaly/issues/889

Closes https://gitlab.com/gitlab-org/gitaly/issues/817

Closes https://gitlab.com/gitlab-org/gitaly/issues/1236

Closes https://gitlab.com/gitlab-org/gitaly/issues/382

This significantly improves performance when a user pushes many references.

project.path_locks.any? doesn't cache the output and runs `SELECT 1 AS one
FROM "path_locks" WHERE project_id = N` each time. When there are thousands
of refs being pushed, this can time out the unicorn worker.

CE port for https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6159.

With text/calendar as Content-Type, the browser always downloads the
content as a file (even ignoring the Content-Disposition header). We
want to display the content inline when accessed from GitLab, similarly
to the RSS feed.