[EE] Move the "Limit conflicts with EE" doc to "Automatic CE-> EE merge"

Signed-off-by: Rémy Coutable <remy@rymai.me>

PROCESS.md

@@ -130,7 +130,8 @@ freeze date (the 7th) should have a corresponding Enterprise Edition merge
 request, even if there are no conflicts. This is to reduce the size of the
 subsequent EE merge, as we often merge a lot to CE on the release date. For more
 information, see
-[limit conflicts with EE when developing on CE][limit_ee_conflicts].
+[Automatic CE->EE merge][automatic_ce_ee_merge] and
+[Guidelines for implementing Enterprise Edition features][ee_features].
 
 ### After the 7th
 
@@ -281,4 +282,5 @@ still an issue I encourage you to open it on the [GitLab.com issue tracker](http
 ["Implement design & UI elements" guidelines]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#implement-design-ui-elements
 [Thoughtbot code review guide]: https://github.com/thoughtbot/guides/tree/master/code-review
 [done]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#definition-of-done
-[limit_ee_conflicts]: https://docs.gitlab.com/ce/development/limit_ee_conflicts.html
+[automatic_ce_ee_merge]: https://docs.gitlab.com/ce/development/automatic_ce_ee_merge.html
+[ee_features]: https://docs.gitlab.com/ce/development/ee_features.html

doc/development/README.md

@@ -16,8 +16,8 @@ comments: false
 - [GitLab core team & GitLab Inc. contribution process](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/PROCESS.md)
 - [Generate a changelog entry with `bin/changelog`](changelog.md)
 - [Code review guidelines](code_review.md) for reviewing code and having code reviewed.
-- [Limit conflicts with EE when developing on CE](limit_ee_conflicts.md)
-- [Guidelines for implementing Enterprise Edition feature](ee_features.md)
+- [Automatic CE->EE merge](automatic_ce_ee_merge.md)
+- [Guidelines for implementing Enterprise Edition features](ee_features.md)
 
 ## UX and frontend guides
 

doc/development/automatic_ce_ee_merge.md

+# Automatic CE->EE merge
+
+GitLab Community Edition is merged automatically every 3 hours into the
+Enterprise Edition (look for the [`CE Upstream` merge requests]).
+
+This merge is done automatically in a
+[scheduled pipeline](https://gitlab.com/gitlab-org/release-tools/-/jobs/43201679).
+If a merge is already in progress, the job [doesn't create a new one](https://gitlab.com/gitlab-org/release-tools/-/jobs/43157687).
+
+**If you are pinged in a `CE Upstream` merge request to resolve a conflict,
+please resolve the conflict as soon as possible or ask someone else to do it!**
+
+>**Note:**
+It's ok to resolve more conflicts than the one that you are asked to resolve. In
+that case, it's a good habit to ask for a double-check on your resolution by
+someone who is familiar with the code you touched.
+
+[`CE Upstream` merge requests]: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests?label_name%5B%5D=CE+upstream
+
+### Always merge EE merge requests before their CE counterparts
+
+**In order to avoid conflicts in the CE->EE merge, you should always merge the
+EE version of your CE merge request first, if present.**
+
+The rationale for this is that as CE->EE merges are done automatically every few
+hours, it can happen that:
+
+1. A CE merge request that needs EE-specific changes is merged
+1. The automatic CE->EE merge happens
+1. Conflicts due to the CE merge request occur since its EE merge request isn't
+  merged yet
+1. The automatic merge bot will ping someone to resolve the conflict **that are
+  already resolved in the EE merge request that isn't merged yet**
+
+That's a waste of time, and that's why you should merge EE merge request before
+their CE counterpart.
+
+## Avoiding CE->EE merge conflicts beforehand
+
+To avoid the conflicts beforehand, check out the
+[Guidelines for implementing Enterprise Edition features](ee_features.md).
+
+In any case, the CI `ee_compat_check` job will tell you if you need to open an
+EE version of your CE merge request.
+
+### Conflicts detection in CE merge requests
+
+For each commit (except on `master`), the `ee_compat_check` CI job tries to
+detect if the current branch's changes will conflict during the CE->EE merge.
+
+The job reports what files are conflicting and how to setup a merge request
+against EE.
+
+#### How the job works
+
+1. Generates the diff between your branch and current CE `master`
+1. Tries to apply it to current EE `master`
+1. If it applies cleanly, the job succeeds, otherwise...
+1. Detects a branch with the `ee-` prefix or `-ee` suffix in EE
+1. If it exists, generate the diff between this branch and current EE `master`
+1. Tries to apply it to current EE `master`
+1. If it applies cleanly, the job succeeds
+
+In the case where the job fails, it means you should create a `ee-<ce_branch>`
+or `<ce_branch>-ee` branch, push it to EE and open a merge request against EE
+`master`.
+At this point if you retry the failing job in your CE merge request, it should
+now pass.
+
+Notes:
+
+- This task is not a silver-bullet, its current goal is to bring awareness to
+  developers that their work needs to be ported to EE.
+- Community contributors shouldn't be required to submit merge requests against
+  EE, but reviewers should take actions by either creating such EE merge request
+  or asking a GitLab developer to do it **before the merge request is merged**.
+- If you branch is too far behind `master`, the job will fail. In that case you
+  should rebase your branch upon latest `master`.
+- Code reviews for merge requests often consist of multiple iterations of
+  feedback and fixes. There is no need to update your EE MR after each
+  iteration. Instead, create an EE MR as soon as you see the
+  `ee_compat_check` job failing. After you receive the final approval
+  from a Maintainer (but **before the CE MR is merged**) update the EE MR.
+  This helps to identify significant conflicts sooner, but also reduces the
+  number of times you have to resolve conflicts.
+- Please remember to
+  [always have your EE merge request merged before the CE version](#always-merge-ee-merge-requests-before-their-ce-counterparts).
+- You can use [`git rerere`](https://git-scm.com/blog/2010/03/08/rerere.html)
+  to avoid resolving the same conflicts multiple times.
+
+---
+
+[Return to Development documentation](README.md)

doc/development/ee_features.md

-# Guidelines for implementing Enterprise Edition feature
+# Guidelines for implementing Enterprise Edition features
 
 - **Write the code and the tests.**: As with any code, EE features should have
   good test coverage to prevent regressions.
@@ -380,3 +380,9 @@ to avoid conflicts during CE to EE merge.
   }
 }
 ```
+
+## gitlab-svgs
+
+Conflicts in `app/assets/images/icons.json` or `app/assets/images/icons.svg` can
+be resolved simply by regenerating those assets with
+[`yarn run svg`](https://gitlab.com/gitlab-org/gitlab-svgs).

doc/development/writing_documentation.md

@@ -142,7 +142,7 @@ tests. If it doesn't, the whole test suite will run (including docs).
 ---
 
 When you submit a merge request to GitLab Community Edition (CE), there is an
-additional job called `rake ee_compat_check` that runs against Enterprise
+additional job called `ee_compat_check` that runs against Enterprise
 Edition (EE) and checks if your changes can apply cleanly to the EE codebase.
 If that job fails, read the instructions in the job log for what to do next.
 Contributors do not need to submit their changes to EE, GitLab Inc. employees

lib/gitlab/ee_compat_check.rb

@@ -280,7 +280,7 @@ module Gitlab
         The `#{branch}` branch applies cleanly to EE/master!
 
         Much ❤️! For more information, see
-        https://docs.gitlab.com/ce/development/limit_ee_conflicts.html#check-the-rake-ee_compat_check-in-your-merge-requests
+        https://docs.gitlab.com/ce/development/automatic_ce_ee_merge.html
         #{THANKS_FOR_READING_BANNER}
       }
     end
@@ -357,7 +357,7 @@ module Gitlab
         Once this is done, you can retry this failed build, and it should pass.
 
         Stay 💪 ! For more information, see
-        https://docs.gitlab.com/ce/development/limit_ee_conflicts.html#check-the-rake-ee_compat_check-in-your-merge-requests
+        https://docs.gitlab.com/ce/development/automatic_ce_ee_merge.html
         #{THANKS_FOR_READING_BANNER}
       }
     end
@@ -378,7 +378,7 @@ module Gitlab
         retry this build.
 
         Stay 💪 ! For more information, see
-        https://docs.gitlab.com/ce/development/limit_ee_conflicts.html#check-the-rake-ee_compat_check-in-your-merge-requests
+        https://docs.gitlab.com/ce/development/automatic_ce_ee_merge.html
         #{THANKS_FOR_READING_BANNER}
       }
     end