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.

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

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.

Since Rails 5 request.format gets set by extension if it's not explicitly
set.
That means artifacts_controller#file no longer works as expected.
This commit explicitly sets request.format for artifacts_controller#file.

Closes #46192

In Rails 4.2 if params[:format] is empty, Rails set it to :html
But since Rails 5.0 the framework now looks for an extension.
E.g. for `blob/master/CHANGELOG.md` in Rails 4 the format would be
`:html`, but in Rails 5 on it'd be `:md`

This commit explicitly sets the `:html` format for all requests unless
`:format` is set by a client e.g. by JS for XHR requests.

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

#close_merge_request_without_source_project -> close_merge_request_if_no_source_project

"Maintainer" will be freed to be used for #42751

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

this required moving some data store actions & mutations around

Signed-off-by: NRémy Coutable <remy@rymai.me>

Signed-off-by: NRémy Coutable <remy@rymai.me>

render job items (needs improvements to components)

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>