Closes #14370

Move gon function into its own helper

Closes #13574

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

Also, improve specs for BambooService

Similar to https://gitlab.com/gitlab-org/gitlab-ce/issues/3515Signed-off-by: NRémy Coutable <remy@rymai.me>

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

To reproduce:

1. Create a project with some content
2. Rename the project
3. Create a new project with the same name.
4. Boom - 404.

After step 2, the branch and tag counts were not being cleared. This would
cause `repository.has_visible_content?` to erroneously return `true`
for the newly-created project.

Closes #13384

See https://gitlab.com/gitlab-org/gitlab-ce/issues/3515

Closes #14963.

Closes #14961

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

GitHub Pull Requests importer handle with the repository while
importing data, we need to make sure that the cached values are valid.

  This problem only was affecting the dev env.

Closes #13957

This will help us to avoid posible merge conflicts when merging
gitlab-ce to gitlab-ee

Rails' "url_helpers" method creates an anonymous Module (which a bunch
of methods) on every call. By caching the output of this method in a
dedicated method we can shave off about 10 seconds of loading time for
an issue with around 200 comments.

These methods are called quite often in loops so by memoizing their
output we can reduce timings a bit.