"new look" causes attach-file to ignore external_url

Summary

Attaching a file to an issue with "New look" enabled (on self-managed gitlab) results in a 404, the subdir from external_url is missing from the URL. It works fine with "New look" disabled.

Steps to reproduce

1. Ensure "New look" is enabled.
2. Create an issue or edit or comment on an existing one.
3. Click on the paperclip icon to attach a file, select a file (does not seem to matter).

Immediately see

The gitlab_configs.rb file includes

external_url 'https://myhost.com/git'

Using the dev-console, the URL https://myhost.com/repogroup/reponame/uploads is missing the /git leading subdir, it should be https://myhost.com/git/repogroup/reponame/uploads.

What is the current bug behavior?

I cannot attach files to the issue with "New look" enabled.

What is the expected correct behavior?

The /uploads link should have included the leading /git subdir.

Expand for output related to GitLab environment info

System information
System:
Current User:   git
Using RVM:      no
Ruby Version:   3.2.5
Gem Version:    3.6.5
Bundler Version:2.6.5
Rake Version:   13.0.6
Redis Version:  7.0.15
Sidekiq Version:7.2.4
Go Version:     unknown

GitLab information
Version:        17.10.3
Revision:       22d4014a923
Directory:      /opt/gitlab/embedded/service/gitlab-rails
DB Adapter:     PostgreSQL
DB Version:     16.8
URL:            https://myhost.com/git
HTTP Clone URL: https://myhost.com/git/some-group/some-project.git
SSH Clone URL:  ssh://git@myhost.com:20027/some-group/some-project.git
Using LDAP:     yes
Using Omniauth: yes
Omniauth Providers:

GitLab Shell
Version:        14.41.0
Repository storages:
- default:      unix:/var/opt/gitlab/gitaly/gitaly.socket
GitLab Shell path:              /opt/gitlab/embedded/service/gitlab-shell

Gitaly
- default Address:      unix:/var/opt/gitlab/gitaly/gitaly.socket
- default Version:      17.10.3
- default Git Version:  2.48.1.gl1
- 

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab subtasks ...
Checking GitLab Shell ...
GitLab Shell: ... GitLab Shell version >= 14.41.0 ? ... OK (14.41.0)
Running /opt/gitlab/embedded/service/gitlab-shell/bin/gitlab-shell-check
Internal API available: OK
Redis available via internal API: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Gitaly ...
Gitaly: ... default ... OK
Checking Gitaly ... Finished
Checking Sidekiq ...
Sidekiq: ... Running? ... yes
Number of Sidekiq processes (cluster/worker) ... 1/1
Checking Sidekiq ... Finished
Checking Incoming Email ...
Incoming Email: ... Checking Reply by email ...
IMAP server credentials are correct? ... Checking git@MyCompany.com
no
Try fixing it:
An error occurred: Net::IMAP::NoResponseError: LOGIN failed.
Check that the information in config/gitlab.yml is correct
For more information see:
doc/administration/reply_by_email.md
Please fix the error above and rerun the checks.
Mailroom enabled? ... skipped
MailRoom running? ... skipped
Checking Reply by email ... Finished
Checking Incoming Email ... Finished
Checking LDAP ...
LDAP: ... Server: ldapmain
LDAP authentication... Success
LDAP users with access to your GitLab server (only showing the first 100 results)
User output sanitized. Found 12 users of 100 limit.
Checking LDAP ... Finished
Checking GitLab App ...
Database config exists? ... yes
Tables are truncated? ... skipped
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Cable config exists? ... yes
Resque config exists? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Systemd unit files or init script exist? ... skipped (omnibus-gitlab has neither init script nor systemd units)
Systemd unit files or init script up-to-date? ... skipped (omnibus-gitlab has neither init script nor systemd units)
Projects have namespace: ...
5/3 ... yes
4/4 ... yes
5/5 ... yes
5/6 ... yes
14/7 ... yes
4/9 ... yes
5/10 ... yes
4/12 ... yes
4/13 ... yes
4/14 ... yes
4/15 ... yes
4/16 ... yes
22/17 ... yes
22/18 ... yes
4/19 ... yes
22/20 ... yes
4/21 ... yes
4/22 ... yes
4/23 ... yes
4/24 ... yes
4/25 ... yes
4/26 ... yes
4/27 ... yes
3/28 ... yes
3/29 ... yes
3/30 ... yes
3/31 ... yes
3/32 ... yes
3/33 ... yes
3/34 ... yes
15/35 ... yes
15/36 ... yes
15/37 ... yes
15/38 ... yes
4/39 ... yes
2/40 ... yes
4/41 ... yes
4/42 ... yes
4/43 ... yes
15/44 ... yes
15/45 ... yes
5/46 ... yes
15/47 ... yes
15/48 ... yes
15/49 ... yes
14/50 ... yes
4/51 ... yes
15/52 ... yes
15/53 ... yes
4/54 ... yes
15/55 ... yes
14/56 ... yes
15/57 ... yes
15/58 ... yes
15/60 ... yes
4/61 ... yes
15/62 ... yes
15/63 ... yes
15/65 ... yes
15/66 ... yes
15/67 ... yes
15/68 ... yes
15/69 ... yes
4/71 ... yes
15/72 ... yes
5/73 ... yes
4/74 ... yes
15/75 ... yes
2/76 ... yes
15/77 ... yes
15/78 ... yes
15/79 ... yes
5/80 ... yes
15/82 ... yes
15/83 ... yes
15/84 ... yes
125/85 ... yes
15/86 ... yes
15/87 ... yes
15/88 ... yes
14/89 ... yes
15/90 ... yes
15/91 ... yes
15/92 ... yes
15/93 ... yes
15/94 ... yes
15/95 ... yes
15/96 ... yes
15/97 ... yes
15/98 ... yes
15/99 ... yes
15/100 ... yes
5/101 ... yes
5/102 ... yes
15/103 ... yes
15/104 ... yes
15/105 ... yes
15/106 ... yes
15/107 ... yes
15/108 ... yes
15/109 ... yes
15/110 ... yes
15/111 ... yes
131/112 ... yes
15/113 ... yes
14/114 ... yes
15/115 ... yes
15/116 ... yes
131/117 ... yes
131/118 ... yes
15/119 ... yes
131/120 ... yes
15/121 ... yes
15/122 ... yes
15/123 ... yes
Redis version >= 6.2.14? ... yes
Ruby version >= 3.0.6 ? ... yes (3.2.5)
Git user has default SSH configuration? ... yes
Active users: ... 10
Is authorized keys file accessible? ... yes
GitLab configured to store new projects in hashed storage? ... yes
All projects are in hashed storage? ... yes
Checking GitLab App ... Finished
Checking GitLab subtasks ... Finished

Possible fixes