Cannot commit to fork from main project if fork is behind

Summary

When a user attempts to commit a change made via the edit button on a main project, and their fork is a few commits behind, the commit will fail with a message Someone edited the file the same time you did. Please check out the file and make sure your changes will not unintentionally remove theirs.

This will happen regardless of whether the user is the only one on that project. Note that this does not happen if the WebIDE button is used - in that case, the file is opened directly in the forked project to be edited.

This issue started after an upgrade to v14.2.5. Customer did not see this happening on v13.9.5.

Steps to reproduce

1. Have a project (e.g. mainproject) that a user does not have write access to
2. The user creates a fork of this project
3. Have main project be a few commits ahead of the user's fork
4. Go to main project, open a file -> Edit
5. Click commit button which says A new branch will be created in your fork and a new merge request will be started.
6. See error message Someone edited the file the same time you did. Please...

What is the current bug behavior?

Commit fails (with an incorrect message?).

What is the expected correct behavior?

Commit is successful OR more appropriate message regarding fork being too far behind.

Relevant logs and/or screenshots

CommitError.log (Doesn't seem to show error?):

/var/log/gitlab/gitlab-rails/production_json.log:{"method":"PUT","path":"/forktest/main/-/update/main/README.md","format":"html","controller":"Projects::BlobController","action":"update","status":200,"time":"2021-11-01T05:43:53.261Z","params":[{"key":"_method","value":"put"},{"key":"authenticity_token","value":"[FILTERED]"},{"key":"file_path","value":"README.md"},{"key":"commit_message","value":"Update README.md"},{"key":"branch_name","value":"mrstrickland-main-patch-09626"},{"key":"create_merge_request","value":"1"},{"key":"original_branch","value":"main"},{"key":"last_commit_sha","value":"ebe991a0028b62bd23f0c459d39d8cc4aea6a6aa"},{"key":"content","value":"[FILTERED]"},{"key":"from_merge_request_iid","value":""},{"key":"namespace_id","value":"forktest"},{"key":"project_id","value":"main"},{"key":"id","value":"main/README.md"}],"remote_ip":"43.243.56.129","user_id":33,"username":"mrstrickland","ua":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36","correlation_id":"01FKD0D0FA64DPYM5AN5SEW88F","meta.user":"mrstrickland","meta.project":"forktest/main","meta.root_namespace":"forktest","meta.caller_id":"Projects::BlobController#update","meta.remote_ip":"43.243.56.129","meta.feature_category":"source_code_management","meta.client_id":"user/33","gitaly_calls":4,"gitaly_duration_s":0.019146,"redis_calls":42,"redis_duration_s":0.012599,"redis_read_bytes":8395,"redis_write_bytes":4603,"redis_cache_calls":41,"redis_cache_duration_s":0.01192,"redis_cache_read_bytes":8174,"redis_cache_write_bytes":3778,"redis_shared_state_calls":1,"redis_shared_state_duration_s":0.000679,"redis_shared_state_read_bytes":221,"redis_shared_state_write_bytes":825,"db_count":44,"db_write_count":0,"db_cached_count":9,"cpu_s":1.06143,"mem_objects":753856,"mem_bytes":77490938,"mem_mallocs":268994,"mem_total_bytes":107645178,"pid":543927,"queue_duration_s":0.034145,"db_duration_s":0.09715,"view_duration_s":0.73386,"duration_s":1.12528}
/var/log/gitlab/gitlab-workhorse/current:{"content_type":"text/html; charset=utf-8","correlation_id":"01FKD0D0FA64DPYM5AN5SEW88F","duration_ms":1229,"host":"gitlab.agounder.com","level":"info","method":"POST","msg":"access","proto":"HTTP/1.1","referrer":"https://gitlab.agounder.com/forktest/main/-/update/main/README.md","remote_addr":"43.243.56.129:0","remote_ip":"43.243.56.129","route":"","status":200,"system":"http","time":"2021-11-01T05:43:53Z","ttfb_ms":1226,"uri":"/forktest/main/-/update/main/README.md","user_agent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36","written_bytes":157327}
/var/log/gitlab/gitaly/current:{"correlation_id":"01FKD0D0FA64DPYM5AN5SEW88F","grpc.code":"OK","grpc.meta.auth_version":"v2","grpc.meta.client_name":"gitlab-web","grpc.meta.deadline_type":"regular","grpc.meta.method_type":"unary","grpc.method":"FindCommit","grpc.request.deadline":"2021-11-01T05:44:22.021Z","grpc.request.fullMethod":"/gitaly.CommitService/FindCommit","grpc.request.glProjectPath":"forktest/main","grpc.request.glRepository":"project-7258","grpc.request.repoPath":"@hashed/b2/bf/b2bf50ecada62994533dcc3197242102a5f1e20bc8acc45f904eb0a2004dfb1f.git","grpc.request.repoStorage":"default","grpc.service":"gitaly.CommitService","grpc.start_time":"2021-11-01T05:43:52.421Z","grpc.time_ms":2.571,"level":"info","msg":"finished unary call with code OK","peer.address":"@","pid":2769221,"remote_ip":"43.243.56.129","span.kind":"server","system":"grpc","time":"2021-11-01T05:43:52.424Z","username":"mrstrickland"}
/var/log/gitlab/gitaly/current:{"correlation_id":"01FKD0D0FA64DPYM5AN5SEW88F","grpc.code":"OK","grpc.meta.auth_version":"v2","grpc.meta.client_name":"gitlab-web","grpc.meta.deadline_type":"regular","grpc.meta.method_type":"server_stream","grpc.method":"TreeEntry","grpc.request.deadline":"2021-11-01T05:44:22.026Z","grpc.request.fullMethod":"/gitaly.CommitService/TreeEntry","grpc.request.glProjectPath":"forktest/main","grpc.request.glRepository":"project-7258","grpc.request.repoPath":"@hashed/b2/bf/b2bf50ecada62994533dcc3197242102a5f1e20bc8acc45f904eb0a2004dfb1f.git","grpc.request.repoStorage":"default","grpc.service":"gitaly.CommitService","grpc.start_time":"2021-11-01T05:43:52.426Z","grpc.time_ms":1.026,"level":"info","msg":"finished streaming call with code OK","peer.address":"@","pid":2769221,"remote_ip":"43.243.56.129","span.kind":"server","system":"grpc","time":"2021-11-01T05:43:52.427Z","username":"mrstrickland"}
/var/log/gitlab/gitaly/current:{"correlation_id":"01FKD0D0FA64DPYM5AN5SEW88F","grpc.code":"OK","grpc.meta.auth_version":"v2","grpc.meta.client_name":"gitlab-web","grpc.meta.deadline_type":"regular","grpc.meta.method_type":"server_stream","grpc.method":"FindCommits","grpc.request.deadline":"2021-11-01T05:44:22.031Z","grpc.request.fullMethod":"/gitaly.CommitService/FindCommits","grpc.request.glProjectPath":"forktest/main","grpc.request.glRepository":"project-7258","grpc.request.repoPath":"@hashed/b2/bf/b2bf50ecada62994533dcc3197242102a5f1e20bc8acc45f904eb0a2004dfb1f.git","grpc.request.repoStorage":"default","grpc.service":"gitaly.CommitService","grpc.start_time":"2021-11-01T05:43:52.431Z","grpc.time_ms":2.345,"level":"info","msg":"finished streaming call with code OK","peer.address":"@","pid":2769221,"remote_ip":"43.243.56.129","span.kind":"server","system":"grpc","time":"2021-11-01T05:43:52.433Z","username":"mrstrickland"}
/var/log/gitlab/gitaly/current:{"correlation_id":"01FKD0D0FA64DPYM5AN5SEW88F","grpc.code":"OK","grpc.meta.auth_version":"v2","grpc.meta.client_name":"gitlab-web","grpc.meta.deadline_type":"regular","grpc.meta.method_type":"server_stream","grpc.method":"FindCommits","grpc.request.deadline":"2021-11-01T05:44:22.079Z","grpc.request.fullMethod":"/gitaly.CommitService/FindCommits","grpc.request.glProjectPath":"mrstrickland/main","grpc.request.glRepository":"project-7260","grpc.request.repoPath":"@hashed/79/8b/798bf980fe3b447993defabab766f08ea559cef763004067554516f57f48ffaa.git","grpc.request.repoStorage":"default","grpc.service":"gitaly.CommitService","grpc.start_time":"2021-11-01T05:43:52.479Z","grpc.time_ms":4.129,"level":"info","msg":"finished streaming call with code OK","peer.address":"@","pid":2769221,"remote_ip":"43.243.56.129","span.kind":"server","system":"grpc","time":"2021-11-01T05:43:52.484Z","username":"mrstrickland"}

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Ubuntu 20.04
Proxy:		no
Current User:	git
Using RVM:	no
Ruby Version:	2.7.2p137
Gem Version:	3.1.4
Bundler Version:2.1.4
Rake Version:	13.0.6
Redis Version:	6.0.14
Git Version:	2.32.0
Sidekiq Version:5.2.9
Go Version:	unknown

GitLab information
Version:	14.2.5-ee
Revision:	72c1da0383a
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	12.6
URL:		https://gitlab.agounder.com
HTTP Clone URL:	https://gitlab.agounder.com/some-group/some-project.git
SSH Clone URL:	git@gitlab.agounder.com:some-group/some-project.git
Elasticsearch:	no
Geo:		yes
Geo node:	Primary
Using LDAP:	yes
Using Omniauth:	yes
Omniauth Providers: saml, azure_activedirectory_v2, azure_activedirectory_v2, group_saml, crowd

GitLab Shell
Version:	13.19.1
Repository storage paths:
- default: 	/var/opt/gitlab/git-data/repositories
GitLab Shell path:		/opt/gitlab/embedded/service/gitlab-shell
Git:		/opt/gitlab/embedded/bin/git

Possible fixes