Using author dropdown to filter commits shows no results

Summary

When going to the commits overview page, selecting a user from the "Search by author" dropdown shows no results.

Steps to reproduce

1. Go to the commits page of a project (ex.: https://gitlab.com/hammie/php-algorithms/-/commits/master?ref_type=heads)
2. Select an author from the "Author" dropdown (ex.: https://gitlab.com/hammie/php-algorithms/-/commits/master?author=Sam%20Hambrouck)
3. Notice how the page says "Your search didn't match any commits."

Example Project

Example project: https://gitlab.com/hammie/php-algorithms/-/commits/master?ref_type=heads

It's an old project, but a public one. I can reproduce it in multiple projects, including a self-hosted Gitlab instance.

What is the current bug behavior?

No results are shown.

You can modify the query to include the authors username, in which case it will display the commits as expected:

https://gitlab.com/hammie/php-algorithms/-/commits/master?author=Hammie

What is the expected correct behavior?

The page shows commits authored by the selected person.

Relevant logs and/or screenshots

Unfiltered:

Filtered:

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

Probably caused by a mismatch between the name used on Gitlab, and the name used to author commits. Gitlab appears to know I created these commits, but cannot find them when looking for commits I created.

A possible solution could be to also search for commits by email, as that should match in most cases.