Outline MR guidelines

CONTRIBUTING.md

@@ -14,6 +14,19 @@ flake8 path/to/file
 
 Check [Git4LHCb](https://twiki.cern.ch/twiki/bin/view/LHCb/Git4LHCb) for more details.
 
+Opening a merge request (MR) is a good way to discuss your changes with others.
+If your code is not yet ready to be reviewed by a Moore responsible, you can
+[mark it 'work in
+progress'](https://docs.gitlab.com/ee/user/project/merge_requests/work_in_progress_merge_requests.html)
+by starting the title with `WIP: `. This can be useful for when you want to ask
+others about specific details your unsure of. Non-WIP MRs will be reviewed
+following the [RTA shifter guidelines][shifterpage].
+
+Each MR should have a short title summarising the changes you've made, such as
+"Add two-body prompt D0 HLT2 lines" or "Fix HLT2 forward tracking bug", and a
+description with more detail. It is useful to see [what Moore responsibles look
+for in a MR before you open your first one][shifterpage].
+
 ## Branches
 
 The `master` branch is used for Run 3 development and data-taking. This is the
@@ -21,3 +34,5 @@ usual branch to open merge requests against.
 
 Some other branches track code from previous campaigns. Open an issue if you're
 unsure what branch to use.
+
+[shifterpage]: https://twiki.cern.ch/twiki/bin/viewauth/LHCb/RealTimeAnalysisShifterChecklist
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