Prepare 7.0.0 release

See merge request gitlab-org/gitlab-workhorse!302

Use the new Gitaly auth scheme (v2)

See merge request gitlab-org/gitlab-workhorse!298

Release GitLab Workhorse 6.1.1

See merge request gitlab-org/gitlab-workhorse!301

Support custom error page override via X-GitLab-Custom-Error

See merge request gitlab-org/gitlab-workhorse!300

make: add INSTALL variable

See merge request gitlab-org/gitlab-workhorse!217

Release GitLab Workhorse v6.1.0

See merge request gitlab-org/gitlab-workhorse!299

Support adding PUT headers for object storage from Rails

See merge request gitlab-org/gitlab-workhorse!297

As revealed in https://gitlab.com/gitlab-org/gitlab-ce/issues/49957, Rails
generates a signed URL with a fixed HTTP header with `Content-Type:
application/octet-stream`. However, if we change or remove that for
some reason in Workhorse, this breaks the upload with a 403 Unauthorized because
the signed URL is not valid.

We can make this more robust by doing the following:

1. In the `/uploads/authorize` request, Rails can return a `StoreHeaders` key-value
pair in the JSON response containing the required headers that the PUT
request must include.
2. Use those HTTP headers if that value is present.
3. For backwards compatibility, if that key is not present, default to
the old behavior of sending the fixed `Content-Type` header.

Lint Workhorse

See merge request gitlab-org/gitlab-workhorse!293

Minor cleanup of gitaly test server

See merge request gitlab-org/gitlab-workhorse!296

Improvements and cleanup to the Makefile

See merge request gitlab-org/gitlab-workhorse!292

Add changelog for 6.0.0

See merge request gitlab-org/gitlab-workhorse!291

Accelerate Maven artifact repository uploads

Closes gitlab-ee#5811

See merge request gitlab-org/gitlab-workhorse!283

Release GitLab Workhorse v5.2.0

See merge request gitlab-org/gitlab-workhorse!288

Add support for GitConfigOptions required for git-receive-pack command

See merge request gitlab-org/gitlab-workhorse!281

Refactor ad-hoc protobuf marshaling in gitaly test server

See merge request gitlab-org/gitlab-workhorse!287

Use gitaly-proto 0.111.0

See merge request gitlab-org/gitlab-workhorse!286

Populate Git Protocol

See merge request gitlab-org/gitlab-workhorse!276

Stop calling 'make' from 'go test'

See merge request gitlab-org/gitlab-workhorse!285

More vendoring updates

See merge request gitlab-org/gitlab-workhorse!280