Fetch repositories with --prune option by default.

This will allow us to not recreate branches that has been deleted on the upstream and the mirror.

Related issue: https://gitlab.com/gitlab-org/gitlab-ee/issues/1277

I've reviewed the code for updating local and remote mirrors also  I've manually tested these features and all looks good.

Here is the description of the `--prune` option:


> --prune
>
> Before fetching, remove any remote-tracking references that no longer exist on the remote. Tags are not subject to pruning if they are fetched only because of the default tag auto-following or due to a --tags option. However, if tags are fetched due to an explicit refspec (either on the command line or in the remote configuration, for example if the remote was cloned with the --mirror option), then they are also subject to 


@brodock do you see any issues when fetching repos for GitLab Geo?

See merge request !110

This will allow us to not recreate branches that has been deleted on the upstream and the mirror.

Fix gitlab_custom_hook dependencies

See merge request !107

Add instrumentation to push hooks

See merge request !106

Related to #22053

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

Use full repository path instead of extracting name

In order to implement nested groups https://gitlab.com/gitlab-org/gitlab-ce/issues/2772 we can not rely on old path with one slash that split namespace and project name like `namespace/project.git`. Now it can be both `namespace/project.git` and `namespace/namespace/namespace/project.git`. Because of that it makes no sense to extract part of full path. Instead we just pass path to API without change and let rails application do parsing/extraction. 
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !102

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

Git LFS remark in readme is no longer correct.

See merge request !101

Re-use the default logger for performance metrics

See #64 for the discussion leading up to this.

See merge request !100

This removes the need for configuring anything extra. To make scraping
easier each line is prefixed by "metrics:".

Fixes #64

Instrument GitLab Shell and log metrics data to a file

See merge request !98

Test against ruby 2.3

Closes #61

See merge request !99

Fix rsync with ionice command building

See merge request !97

Fix short circuit logic between rsync with and without ionice for storage migrations

See merge request !96

storage migrations

Re-exposing GL_ID to custom hooks

closes https://gitlab.com/gitlab-org/gitlab-ee/issues/995
closes https://gitlab.com/gitlab-org/gitlab-shell/issues/53

See merge request !95

Update VERSION

Was this an oversight? Should we re-tag v3.6.2? Or just bump to v3.6.3?

See merge request !94

Enable GIT_TRACE_PERFORMANCE through a config variable.

The value of the variable must an absolute path needs to exist so we’re able to check if we can write in that file. Because in the 
case we cannot write we’ll throw a warning to the output of the users.

```sh
~/dev/gitlab/local/pacoguzman/gitlab-ce (master=)$ git push origin master
warning: could not open '/wadus' for tracing: Permission denied
Everything up-to-date
```

Closes #59

See merge request !91

Enable GIT_TRACE/GIT_TRACE_PACKET/GIT_TRACE_PERFORMANCE by providing the git_trace_log_file config key

The value of the variable if present must be a writable absolute path. If it’s
not the case we log a proper message and not enable tracing to not throw output to the users.

Set a low IO priority for storage moves to lower performance impact

See merge request !92

Added LFS support to SSH

Required changes to GitLab Shell include the actual handling of the `git-lfs-authenticate` command and the retrieval of the correct credentials.

Needed for gitlab-org/gitlab-ce!6043

Related to gitlab-org/gitlab-ce#3589

> **Note:** gitlab-org/gitlab-ce!6043 needs to be merged before this one.

cc @jacobvosmaer-gitlab @marin @DouweM

See merge request !86