Dropdown menu partially hidden in commit pages

Summary

Looks like the z-index is missing for the dropdown menu in commit pages:

Dropdown partially hidden (from gitlab-tests/new-project@7f993a6d):

Normal behavior (from https://gitlab.com/gitlab-org/gitlab-ce/commit/71b89a87442f7a03387376fff60df8ba2233260b):

Steps to reproduce

n/a

Example Project

Linked above

What is the current bug behavior?

the dropdown is partially hidden

What is the expected correct behavior?

the dropdown is fully visible

Relevant logs and/or screenshots

^

Possible fixes

Fix the z-index. Without it, looks like:

With the z-index set to 9999, it looks like it solves the problem (in the browser web inspector):

cc/ @annabeldunstone