when params[:ref_name] is set to "" by passing an empty query parameter
to the api it is evaluated as false by the || operator.
The use of active support core extensions presence method fixes the original
implemantation.

https://guides.rubyonrails.org/active_support_core_extensions.html#presence

Use correct parent when committing in WebIDE

See merge request gitlab-org/gitlab-ce!29598

When passing start_branch on committing from the WebIDE, it's possible
that the branch has changed since editing started, which results in the
change being applied on top of the latest commit in the branch and
overwriting the new changes.

By passing the start_sha instead we can make sure that the change is
applied on top of the commit which the user started editing from.

This MR refactor RedisCounter and WebIdeCommitsCounter
to be reused by other components.

We're adding more redis base counters to the web ide and other
classes. We're refactoring this class in other to use the logic
in other places.

This extends POST#:id/repository/commits to allow the optional parameter
`:start_project`, which will allow targeting other projects besides the
one derived from `:id`.

Resolves https://gitlab.com/gitlab-org/gitlab-ce/issues/50850

When `force` is set to `true` and `start_branch` is set, the
branch will be ovewritten with the new commit based on the
`HEAD` of the `start_branch`.

This commit includes changes to update the `gitaly-proto` gem.

Don't allow non-members to see private related MRs

Closes #2787

See merge request gitlab/gitlabhq!2866