Fix icon for submodules in merge requests

Summary

In commits and merge requests, Git submodules use a generic file type icon, which is not consistent with the repository view.

Steps to reproduce

  1. Add/change/remove a Git submodule from a repository
  2. View the file list in a commit or merge request

Example Project

What is the current bug behavior?

Submodules use a generic file type icon, which is not consistent with the repository view (see below).

Commit Merge request
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What is the expected correct behavior?

Submodules should use the corresponding file type icon, as seen in the repository (example: https://gitlab.com/gitlab-org/gitlab-test)

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Output of checks

This bug happens on GitLab.com

Edited by André Luís (no longer at GitLab)