Introduce a more-complete implementation of bin/authorized_keys

Closes #118

See merge request gitlab-org/gitlab-shell!178

bin/authorized_keys doesn't check that the requesting user matches the expected
user, so to enable database authorized keys lookups, we currently ask the admin
to create a custom script for that purpose.

Better is to have a complete script that can perform the whole task. This commit
introduces bin/gitlab-shell-authorized-keys-check which does so.

Remove unused redis bin configuration.

Closes #114

See merge request gitlab-org/gitlab-shell!177

Prints a message if project was renamed

See merge request gitlab-org/gitlab-shell!175

Use 'git clone --no-local' when creating a fork

See merge request gitlab-org/gitlab-shell!176

Add a 'fork-repository' command that works with hashed storage

Closes #116

See merge request gitlab-org/gitlab-shell!174

The existing 'fork-project' command cannot work with hashed storage as
the source project basename differs from the destination repository
basename. It is deprecated by the addition of 'fork-repository' and should
be removed in the next major version.

Add relative git object dir envvars to check access request

See merge request gitlab-org/gitlab-shell!171

translate gl_username -> REMOTE_USER

See merge request gitlab-org/gitlab-shell!158

Update version to 9.5.2

See merge request gitlab-org/gitlab-shell!170

pre-receive: Fix undefined local variable error

Closes #108

See merge request gitlab-org/gitlab-shell!169

This was broken during the refactor in c658360e.

Bumps gitlab shell version to 5.9.1

See merge request gitlab-org/gitlab-shell!168

Adds --force option to push branches.

See merge request gitlab-org/gitlab-shell!167

Gitaly redis refactor

Closes gitaly#522

See merge request !164

Support new /internal/post-receive API endpoint

Closes gitaly#522

See merge request !163

Support old versions of ruby without a monotonic clock

Closes #69

See merge request !161