Add an error message when using shell commands with incompatible GitLab versions

Closes #48

See merge request !70

Allow GitLab Shell to check for allowed access based on the used Git protocol.

Needed for gitlab-org/gitlab-ce!4696 and gitlab-org/gitlab-ce#18601

See merge request !62

Remove hound config

Since we moved to gitlab.com we don't use Hound CI anymore. Instead we have rubocop.

See merge request !69

Use STDERR to output error messages

It's pretty minor change so I don't think we need a changelog item for this. 

Fixes https://gitlab.com/gitlab-org/gitlab-shell/issues/47

See merge request !68

Implement shard paths handling

See https://gitlab.com/gitlab-org/gitlab-ee/issues/583

See merge request !61

Prevent blocking custom hook output streams

Based on https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/49

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/1458

See merge request !67

Put Redis loading code in one place

Before this change you could not run the gitlab_net specs in isolation.

See merge request !64

ARGF does more than we want

ARGF is a virtual IO stream that treats the elements of ARGV as paths
to files to be opened. In practice, git-receive-pack will probably
never pass arguments to pre-receive and post-receive because it is not
supposed to (according to 'man 5 githooks'). In case it does, however
our hooks should not have the surprise behavior of treating those
arguments as files to be opened.

See merge request !66

ARGF is a virtual IO stream that treats the elements of ARGV as paths
to files to be opened. In practice, git-receive-pack will probably
never pass arguments to pre-receive and post-receive because it is not
supposed to (according to 'man 5 githooks'). In case it does, however
our hooks should not have the surprise behavior of treating those
arguments as files to be opened.

Simplify the GitAccessStatus class

Make the optional 'message' argument required. Remove unused 'to_json'
method.

See merge request !65

Make the optional 'message' argument required. Remove unused 'to_json'
method.

Update PostReceive worker to provide enqueued_at time

See merge request !63

Use Redis Ruby client instead of shelling out to redis-cli

Previously the post-receive hook fired redis-cli, but if the argument list was too long the hook would silently fail. Instead of shelling out to redis-cli, we use a Ruby client to send the same message.

Closes gitlab-org/gitlab-ce#17329


See merge request !59

`make update-redis` will clone the library and adjust the paths properly

Closes gitlab-org/gitlab-ce#17329

Remove broken badge

The state is shown on the repository anyway

See merge request !39

Fix spelling mistakes in README.md



See merge request !57

Remove the update-head command since GitLab doesn't use it anymore

It looks like we tend to remove commands that are not used by GitLab anymore (see gitlab-org/gitlab-shell!26) and the `update-head` command will soon be in that case (see https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3705), so I think we should remove it from here too.

Note: I'm setting this as a WIP to ensure this doesn't get merged since the GitLab MR is not merged at that moment.

See merge request !51

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