Draft: Allow CI_JOB_TOKEN to push to the same repository

EDIT: superseded by !152096 (merged)

What does this MR do and why?

Allows CI Job to commit results into repository (#389060 (closed)).

Based on the code from #389060 (comment 1265554578)

diff --git a/lib/gitlab/auth.rb b/lib/gitlab/auth.rb
index 06bdb2c1ddce..61e6ced9022e 100644
--- a/lib/gitlab/auth.rb
+++ b/lib/gitlab/auth.rb
@@ -326,6 +326,7 @@ def build_authentication_abilities
         [
           :read_project,
           :build_download_code,
+          :build_push_code,
           :build_read_container_image,
           :build_create_container_image,
           :build_destroy_container_image
diff --git a/lib/gitlab/git_access.rb b/lib/gitlab/git_access.rb
index 35b330fa0894..d33ffb145fb8 100644
--- a/lib/gitlab/git_access.rb
+++ b/lib/gitlab/git_access.rb
@@ -230,7 +230,7 @@ def check_authentication_abilities!
           raise ForbiddenError, error_message(:auth_download)
         end
       when *PUSH_COMMANDS
-        unless authentication_abilities.include?(:push_code)
+        unless authentication_abilities.include?(:push_code) || authentication_abilities.include?(:build_push_code)
           raise ForbiddenError, error_message(:auth_upload)
         end
       end
@@ -340,7 +340,8 @@ def check_change_access!
       if changes == ANY
         can_push = deploy_key? ||
           user_can_push? ||
-          project&.any_branch_allows_collaboration?(user_access.user)
+          project&.any_branch_allows_collaboration?(user_access.user) ||
+          authentication_abilities.include?(:build_push_code) && user_can_push?

         unless can_push
           raise ForbiddenError, error_message(:push_code)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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