Files uploaded to repository have spaces in names replaced with underscores

Summary

Spaces in file names are replaced with underscores, when the file is uploaded to a repo via the directory browser's "+" > "This directory" > "Upload file" dialog.

Steps to reproduce

1. Go to your project's "Project > Details" or "Repository > Files" page.
2. Click the "+" dropdown to the right of the current directory's name (in the directory browser's breadcrumb line).
3. Select "This directory" > "Upload file".
4. In the dialog that pops up, select a local file that has spaces in the name, e.g. "good cats.gif", and upload it. (Commit message doesn't matter.)
5. Behold! Gitlab has uploaded a file called "good_cats.gif" instead of "good cats.gif".

Example Project

https://gitlab.com/ethanherbertson/gitlab-bug-spaces-in-filenames/

The GIF in the above project was uploaded as "good cat.gif", but GitLab silently changed it to "good_cat.gif" instead.

What is the current bug behavior?

A file named "good cat.gif" is uploaded as "good_cat.gif" instead, with no warning or confirmation.

What is the expected correct behavior?

Ideally, a file named "good cat.gif" would be uploaded as "good cat.gif".

Much less preferably, a warning should be present in the upload dialog that the spaces will be changed.

Relevant logs and/or screenshots

Output of checks

N/A

Results of GitLab environment info

Expand for output related to GitLab environment info

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Results of GitLab application Check

Expand for output related to the GitLab application check

N/A

Possible fixes

N/A