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.

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

This commit introduces Releases API under /api/v4/projects/:id/releases

* We are introducing release policies at project level.
* We are deprecating releases changes from tags, both api and web
interface.
* Tags::CreateService no longer create a release

This feature is controlled by :releases_page feature flag

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Previously the string was spanning multiple lines and included a
needless `\n` character in the resulting error message.

This change also reduces duplication by assigning two variables.

This allows users to add patches as attachments to merge request
created via email.

When an email to create a merge request is sent, all the attachments
ending in `.patch` will be applied to the branch specified in the
subject of the email. If the branch did not exist, it will be created
from the HEAD of the repository.

When the patches could not be applied, the error message will be
replied to the user.

The patches can have a maximum combined size of 2MB for now.

Authorisation is done in to Tags::CreateService