Merge branch 'docs-tech-debt-followup-issues' into 'master'

When to create follow-up technical debt issues

See merge request gitlab-org/gitlab-ce!22384

doc/development/contributing/issue_workflow.md

@@ -356,6 +356,45 @@ for a release by the appropriate person.
 Make sure to mention the merge request that the ~"technical debt" issue or
 ~"UX debt" issue is associated with in the description of the issue.
 
+## Technical debt in follow-up issues
+
+It's common to discover technical debt during development of a new feature. In
+the spirit of "minimum viable change", resolution is often deferred to a
+follow-up issue. However, this cannot be used as an excuse to merge poor-quality
+code that would otherwise not pass review, or to overlook trivial matters that
+don't deserve the be scheduled independently, and would be best resolved in the
+original merge request - or not tracked at all!
+
+The overheads of scheduling, and rate of change in the GitLab codebase, mean
+that the cost of a trivial technical debt issue can quickly exceed the value of
+tracking it. This generally means we should resolve these in the original merge
+request - or simply not create a follow-up issue at all.
+
+For example, a typo in a comment that is being copied between files is worth
+fixing in the same MR, but not worth creating a follow-up issue for. Renaming a
+method that is used in many places to make its intent slightly clearer may be
+worth fixing, but it should not happen in the same MR, and is generally not
+worth the overhead of having an issue of its own. These issues would invariably
+be labelled `~P4 ~S4` if we were to create them.
+
+More severe technical debt can have implications for development velocity. If
+it isn't addressed in a timely manner, the codebase becomes needlessly difficult
+to change, new features become difficult to add, and regressions abound.
+
+Discoveries of this kind of technical debt should be treated seriously, and
+while resolution in a follow-up issue may be appropriate, maintainers should
+generally obtain a scheduling commitment from the author of the original MR, or
+the engineering or product manager for the relevant area. This may take the form
+of appropriate Priority / Severity labels on the issue, or an explicit milestone
+and assignee.
+
+The maintainer must always agree before an outstanding discussion is resolved in
+this manner, and will be the one to create the issue. The title and description
+should be of the same quality as those created
+[in the usual manner](#technical-and-ux-debt) - in particular, the issue title
+**must not** begin with `Follow-up`! The creating maintainer should also expect
+to be involved in some capacity when work begins on the follow-up issue.
+
 ## Stewardship
 
 For issues related to the open source stewardship of GitLab,