So we can keep showing it to a user in his project page.

The helper creates a fork of a project with all provided attributes,
but skipping the creation of the repository on disk.

When no fork network exists for the source projects, we create a new
one with the correct source

In GitLab EE, a GitLab instance can be read-only (e.g. when it's a Geo
secondary node). But in GitLab CE it also might be useful to have the
"read-only" idea around. So port it back to GitLab CE.

Also having the principle of read-only in GitLab CE would hopefully
lead to less errors introduced, doing write operations when there
aren't allowed for read-only calls.

Closes gitlab-org/gitlab-ce#37534.

Because of a change in GitLab 9.5.4 to prevent users from assuming control of
a repository already on disk, the import task broke. Imports would fail with
the message, "There is already a repository with that name on disk".

This change skips the validation when the import is done from the
command-line.

Closes #37682

This ensures the open issues/MR count caches are refreshed properly when
creating new issues or MRs. This MR also includes a change to the cache
keys to ensure all caches are rebuilt on the fly.

This particular problem was not caught in the test suite due to a null
cache being used, resulting in all calls that would use a cache using
the underlying data directly. In production the code would fail because
a newly saved record returns an empty hash in #changes meaning checks
such as `state_changed? || confidential_changed?` would return false for
new rows, thus never updating the counters.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/38061

This enables skipping a lesser housekeeping task
(incremental or full repack) by consistently
scheduling a higher task (respectively full repack or gc)
with the same period.
Cf. #34981

There are some redundancies in the validation steps, and that is to
preserve current error messages behavior

Also few specs have to be changed in order to fix madness in validation
logic.

Only admins have the ability to create a project in another user's personal
namespace. Prior to this commit, we were explicitly adding them as masters to
the project. However, admins already have access (by virture of being admins),
so this is unnecessary.

So that whenever we want to reserve more, we're aware,
and don't mess it up.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13766

* Rename AfterImportService
* Use constants
* Move Git operations to Gitlab::Git::Repository
* Use Regexp.union

take the advantage that if they're not used, we
could garbage collect those data, reducing memory
footprint.

Every project page displays a navigation menu that in turn displays the
number of open issues and merge requests. This means that for every
project page we run two COUNT(*) queries, each taking up roughly 30
milliseconds on GitLab.com. By caching these numbers and refreshing them
whenever necessary we can reduce loading times of all these pages by up
to roughly 60 milliseconds.

The number of open issues does not include confidential issues. This is
a trade-off to keep the code simple and to ensure refreshing the data
only needs 2 COUNT(*) queries instead of 3. A downside is that if a
project only has 5 confidential issues the counter will be set to 0.

Because we now have 3 similar counting service classes the code
previously used in Projects::ForksCountService has mostly been moved to
Projects::CountService, which in turn is reused by the various service
classes.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36622

Fix positive raise_error expectation without specifying the error type expected in Project::DestroyService specs

The number of forks of a project doesn't change very frequently and
running a COUNT(*) every time this information is requested can be quite
expensive. We also end up running such a COUNT(*) query at least twice
on the homepage of a project.

By caching this data and refreshing it when necessary we can reduce
project homepage loading times by around 60 milliseconds (based on the
timings of https://gitlab.com/gitlab-org/gitlab-ce).

First round of review, main changes:
- templates.title is human readable, #name will be passed around
- GitLabProjectImporterService has been renamed