This brings back some of the changes in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20099/diffs

For users using Gitaly on top of NFS, accessing the Git data directly
via Rugged is more performant than Gitaly. This merge request introduces
the feature flag `rugged_tree_entry` to activate the Rugged method.

Part of four Rugged changes identified in
https://gitlab.com/gitlab-org/gitlab-ce/issues/57317.

This commit, introduced in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23812,
fixes a problem creating a displaying image diff notes when the image
is stored in LFS. The main problem was that `Gitlab::Diff::File` was
returning an invalid valid in `text?` for this kind of files.

It also fixes a rendering problem with other LFS files, like text
ones. They LFS pointer shouldn't be shown when LFS is enabled
for the project, but they were.

This reverts merge request !23229

This reverts merge request !23140

Now only the data was shown of the service, which is not valueable at
times given some of those expose a lot of RPCs.

Enables frozen string for the following:

* lib/gitlab/fogbugz_import/**/*.rb
* lib/gitlab/gfm/**/*.rb
* lib/gitlab/git/**/*.rb
* lib/gitlab/gitaly_client/**/*.rb
* lib/gitlab/gitlab_import/**/*.rb
* lib/gitlab/google_code_import/**/*.rb
* lib/gitlab/gpg/**/*.rb
* lib/gitlab/grape_logging/**/*.rb
* lib/gitlab/graphql/**/*.rb
* lib/gitlab/graphs/**/*.rb
* lib/gitlab/hashed_storage/**/*.rb
* lib/gitlab/health_checks/**/*.rb

Partially address gitlab-org/gitlab-ce#47424.

Having this in a concern allows us to reuse it for different single
purpose classes that call out to git without going through the
repository every time.

This saves about 128 MB of baseline RAM usage per Unicorn and
Sidekiq process (!).

Linguist wasn't detecting languages anymore from CE/EE since
9ae8b574. However, Linguist::BlobHelper
was still being depended on by BlobLike and others.

This removes the Linguist gem, given it isn't required anymore.
EscapeUtils were pulled in as dependency, but given Banzai depends on
it, it is now added explicitly.

Previously, Linguist was used to detect the best ACE mode. Instead,
we rely on ACE to guess the best mode based on the file extension.

Closes https://gitlab.com/gitlab-org/gitaly/issues/310

The lib/gitlab/git/repository.rb needs to have the same content between
gitlab-ce and gitlab-ee in order to have Gitaly working fine.

Closes gitaly#985

Closes gitaly#921

Closes #42249

Given the priorities shifted for the Gitaly team, this endpoint does not
get a dedicated endpoint yet. To make it work in a cloud native
environment the request needs to go to Gitaly, not rugged. This is
achieved by rerouting to the generic TreeEntry endpoint.

This endpoint still has to be migrated, and this comment makes sure
everyone knows we are aware of this one.

[ci skip]

After installing a new gem, batch-loader, a construct can be used to
queue data to be fetched in bulk. The gem was also introduced in both
gitlab-org/gitlab-ce!14680 and gitlab-org/gitlab-ce!14846, but those mrs
are not merged yet.

For the generation of diffs, both the old blob and the new blob need to
be loaded. This for every file in the diff, too. Now we collect all
these so we do 1 fetch. Three `.allow_n_plus_1_calls` have been removed,
which I expect to be valid, but this needs to be confirmed by a full CI
run.

Possibly closes:
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37445
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37599
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37431

Adds a rubocop rule (with autocorrect) to ensure line break after guard clauses.

Gitlab::Git::Blob.batch_lfs_metadata can be used to check for LFS pointers. It uses a lazy enumorator and filters by blob size

In gitlab-org/gitlab-ee!2976, we saw that a given OID could point
to a commit, which would cause the delta size check to fail.
Gitaly already returns nil if the OID isn't a blob, so this change
makes the Rugged implementation consistent.

remove some lint

An upcoming update to rubocop-gitlab-security added additional
violations.