Don't allow group runners to be assigned to projects via admin

Summary

When editing a group runner via the admin panel, there is a section for "Restrict projects for this Runner" where you can enable projects for the group runner. However, group runners cannot be assigned to projects, so when you enable a project for a group runner, you get a generic 500 page with no error. This section should be hidden when editing a group runner because enabling a project for a group runner is not supported and results in an error.

Steps to reproduce

1. Register a runner for a specific group
2. Go to the admin panel -> Runners (/admin/runners)
3. Click on Edit for the Group Runner
4. On this edit screen (/admin/runners/:id), select Enable for a project in the Restrict projects for this Runner
5. Get generic 500 error screen

What is the current bug behavior?

On the admin edit runner screen (/admin/runners/:id) for a group runner, when you enable a project in the section "Restrict projects for this Runner", it results in a 500 error page as assigning a group runner to a project is not supported.

What is the expected correct behavior?

On the admin edit runner screen (/admin/runners/:id) for a group runner, the section "Restrict projects for this Runner" should not be shown as group runners cannot be assigned to projects and results in an error.

Relevant logs and/or screenshots

Screenshot of the edit runner page for a group runner:

Screenshot of 500 error page when you enable a project for a group runner:

Output of checks

(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Ubuntu 16.04
Proxy:		no
Current User:	git
Using RVM:	no
Ruby Version:	2.4.4p296
Gem Version:	2.7.6
Bundler Version:1.16.2
Rake Version:	12.3.1
Redis Version:	3.2.12
Git Version:	2.18.1
Sidekiq Version:5.2.1
Go Version:	unknown
GitLab information
Version:	11.4.0-ee
Revision:	cfe266c
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
DB Version:	9.6.8
URL:		http://198.199.92.126
HTTP Clone URL:	http://198.199.92.126/some-group/some-project.git
SSH Clone URL:	git@198.199.92.126:some-group/some-project.git
Elasticsearch:	no
Geo:		no
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers:
GitLab Shell
Version:	8.3.3
Repository storage paths:

• default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab Shell ...
GitLab Shell version >= 8.3.3 ? ... OK (8.3.3)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
46/1 ... repository is empty
46/2 ... repository is empty
46/3 ... repository is empty
46/4 ... repository is empty
47/5 ... repository is empty
47/6 ... repository is empty
47/8 ... repository is empty
47/9 ... repository is empty
47/10 ... repository is empty
47/11 ... ok
48/12 ... repository is empty
48/13 ... repository is empty
48/14 ... repository is empty
48/15 ... repository is empty
48/16 ... repository is empty
48/17 ... repository is empty
49/18 ... repository is empty
49/19 ... repository is empty
49/20 ... repository is empty
49/21 ... repository is empty
49/22 ... ok
49/23 ... repository is empty
49/24 ... repository is empty
49/25 ... repository is empty
49/26 ... repository is empty
49/27 ... repository is empty
50/28 ... repository is empty
50/29 ... repository is empty
50/30 ... repository is empty
50/31 ... repository is empty
50/32 ... repository is empty
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50/34 ... repository is empty
51/35 ... repository is empty
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51/37 ... repository is empty
51/38 ... repository is empty
51/39 ... repository is empty
51/40 ... repository is empty
51/41 ... repository is empty
51/42 ... repository is empty
51/43 ... repository is empty
52/44 ... repository is empty
52/45 ... repository is empty
52/46 ... repository is empty
52/47 ... repository is empty
52/48 ... repository is empty
52/49 ... repository is empty
52/50 ... repository is empty
52/51 ... repository is empty
53/52 ... repository is empty
53/53 ... repository is empty
53/54 ... repository is empty
53/55 ... repository is empty
53/56 ... repository is empty
53/57 ... repository is empty
53/58 ... repository is empty
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54/60 ... repository is empty
54/61 ... repository is empty
54/62 ... repository is empty
55/63 ... repository is empty
55/64 ... repository is empty
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58/74 ... repository is empty
58/75 ... repository is empty
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58/77 ... repository is empty
58/78 ... repository is empty
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59/80 ... repository is empty
59/81 ... repository is empty
59/82 ... repository is empty
59/83 ... repository is empty
59/84 ... repository is empty
59/85 ... repository is empty
60/86 ... repository is empty
60/87 ... repository is empty
60/88 ... repository is empty
60/89 ... repository is empty
60/90 ... ok
1/91 ... repository is empty
60/92 ... ok
1/93 ... repository is empty
83/94 ... repository is empty
83/95 ... repository is empty
83/96 ... repository is empty
84/97 ... repository is empty
84/98 ... repository is empty
84/99 ... repository is empty
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86/108 ... repository is empty
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87/110 ... repository is empty
88/111 ... repository is empty
88/112 ... repository is empty
88/113 ... repository is empty
89/114 ... repository is empty
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90/116 ... repository is empty
90/117 ... repository is empty
90/118 ... repository is empty
90/119 ... repository is empty
91/120 ... repository is empty
91/121 ... repository is empty
91/122 ... repository is empty
91/123 ... repository is empty
91/124 ... repository is empty
98/125 ... repository is empty
91/126 ... ok
110/127 ... repository is empty
60/128 ... repository is empty
60/129 ... repository is empty
60/130 ... repository is empty
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Reply by email is disabled in config/gitlab.yml
Checking LDAP ...
LDAP is disabled in config/gitlab.yml
Checking LDAP ... Finished
Checking GitLab ...
Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... 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
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
46/1 ... yes
46/2 ... yes
46/3 ... yes
46/4 ... yes
47/5 ... yes
47/6 ... yes
47/8 ... yes
47/9 ... yes
47/10 ... yes
47/11 ... yes
48/12 ... yes
48/13 ... yes
48/14 ... yes
48/15 ... yes
48/16 ... yes
48/17 ... yes
49/18 ... yes
49/19 ... yes
49/20 ... yes
49/21 ... yes
49/22 ... yes
49/23 ... yes
49/24 ... yes
49/25 ... yes
49/26 ... yes
49/27 ... yes
50/28 ... yes
50/29 ... yes
50/30 ... yes
50/31 ... yes
50/32 ... yes
50/33 ... yes
50/34 ... yes
51/35 ... yes
51/36 ... yes
51/37 ... yes
51/38 ... yes
51/39 ... yes
51/40 ... yes
51/41 ... yes
51/42 ... yes
51/43 ... yes
52/44 ... yes
52/45 ... yes
52/46 ... yes
52/47 ... yes
52/48 ... yes
52/49 ... yes
52/50 ... yes
52/51 ... yes
53/52 ... yes
53/53 ... yes
53/54 ... yes
53/55 ... yes
53/56 ... yes
53/57 ... yes
53/58 ... yes
53/59 ... yes
54/60 ... yes
54/61 ... yes
54/62 ... yes
55/63 ... yes
55/64 ... yes
56/65 ... yes
56/66 ... yes
56/67 ... yes
57/68 ... yes
57/69 ... yes
57/70 ... yes
57/71 ... yes
57/72 ... yes
57/73 ... yes
58/74 ... yes
58/75 ... yes
58/76 ... yes
58/77 ... yes
58/78 ... yes
59/79 ... yes
59/80 ... yes
59/81 ... yes
59/82 ... yes
59/83 ... yes
59/84 ... yes
59/85 ... yes
60/86 ... yes
60/87 ... yes
60/88 ... yes
60/89 ... yes
60/90 ... yes
1/91 ... yes
60/92 ... yes
1/93 ... yes
83/94 ... yes
83/95 ... yes
83/96 ... yes
84/97 ... yes
84/98 ... yes
84/99 ... yes
84/100 ... yes
85/101 ... yes
85/102 ... yes
85/103 ... yes
86/104 ... yes
86/105 ... yes
86/106 ... yes
86/107 ... yes
86/108 ... yes
87/109 ... yes
87/110 ... yes
88/111 ... yes
88/112 ... yes
88/113 ... yes
89/114 ... yes
89/115 ... yes
90/116 ... yes
90/117 ... yes
90/118 ... yes
90/119 ... yes
91/120 ... yes
91/121 ... yes
91/122 ... yes
91/123 ... yes
91/124 ... yes
98/125 ... yes
91/126 ... yes
110/127 ... yes
60/128 ... yes
60/129 ... yes
60/130 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.4.4)
Git version >= 2.9.5 ? ... yes (2.18.1)
Git user has default SSH configuration? ... yes
Active users: ... 78
Elasticsearch version 5.1 - 5.5? ... skipped (elasticsearch is disabled)
Checking GitLab ... Finished

Possible fixes

Remove the assigned projects list if it is a group runner. We should do this in conjunction with our first iterations of #299758 (closed).