Propose a common taxonomy for issue and pr labels

Propose a new spec that desacribes a common label taxonomy to be
applied to (all/many of) our GitHub repositories. This will permit us
to more effectively use labels as part of our planning process.

Part of CCI-MOC/ops-issues#270

specs/0006-label-taxonomy.md

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+# A Taxonomy for Issue and PR Labels
+
+This is a proposal for formalizing the labels we use in our
+repositories in order to make them more meaningful and more useful.
+
+## Problem Description
+
+We use issue and pull request labels to indicate certain metadata
+about these items. Some labels are used to position an issue along a
+scale (is this high or low priority? Is this a big or small issue?).
+Other labels are used to group together issues that share some common
+aspect ("These are website issues" or "These issues need better
+descriptions").
+
+Our collection of labels has grown organically over time, and as we
+have created new labels they have not always been propagated to all
+of our repositories. This leads to two problems:
+
+- We can't always use labels effectively in our sprint planning
+  because sometimes the labels aren't available when we want them.
+
+- It can be difficult to differentiate between different types of
+  labels.
+
+## Policy
+
+I would like to propose a common label taxonomy to adopt across all of
+our repositories. The labels will be organized around several axes,
+indicated by prefixes on the label name. For example, labels that
+indicate priority will live on the `priority` axis, and will be
+named like `priority/critical` or `priority/medium`. We should start
+with the following axes that cover most of our existing labels:
+
+- **Type**
+
+  The `type` axis describes in general terms the sort of work required
+  to resolve the issue.
+
+  - `type/bug`
+  - `type/enhancement`
+  - `type/documentation`
+  - `type/research`
+  - `type/discussion`
+
+- **Status**
+
+  The `status` axis describes the current condition of the issue or
+  pull request. This is a multi-valued axis (e.g., an issue may be
+  both `accepted` and `blocked`).
+
+  - `status/blocked`
+  - `status/wontfix`
+  - `status/invalid`
+  - `status/accepted`
+
+- **Topic**
+
+  The `topic` axis is groups to group issues and pull requests that
+  share some common aspect.
+
+  - `topic/monitoring`
+  - `topic/gitops`
+  - `topic/policy`
+  - `topic/mghpcc`
+  - `topic/website`
+
+- **Flag**
+
+  The `flag` axis is used to draw attention to an issue or pull
+  request.
+
+  - `flag/help wanted`
+  - `flag/needs description`
+  - `flag/added post planning`
+  - `flag/good first issue`
+  - `flag/question`
+
+- **Priority**
+
+  The `priority` axis is used to describe the criticality of an issue
+  or pull request.
+
+  - `priority/medium`
+  - `priority/high`
+  - `priority/critical`
+
+As soon as
+[cci-moc/ops-issues#241](https://github.com/CCI-MOC/ops-issues/issues/241)
+is complete we will also add something analogous to a `size` or
+`effort` axis.
+
+## Alternatives & History
+
+None
+
+## Implementation
+
+### Author(s)
+
+Primary author:
+  - Lars Kellogg-Stedman <[email protected]>
+
+Other contributors:
+  - None
+
+### Milestones
+
+This policy will go into effect as soon as this policy is approved by
+the ops team.
+
+### Work Items
+
+- Configure tooling to apply our label taxonomy to all repositories
+  involved in our project planning processes.
+
+## References
+
+Several people have written about label taxonomies specifically in the
+context of GitHub:
+
+
+- [Sane Github
+  Labels](https://medium.com/@dave_lunny/sane-github-labels-c5d2e6004b63),
+  by Dave Lunny
+- [GitHub Labels that are logical, colorful and
+  sensible](https://seantrane.com/posts/logical-colorful-github-labels-18230/),
+  by Sean Trane Sciarrone
+- [How we organize GitHub issues: A simple styleguide for
+  tagging](https://robinpowered.com/blog/best-practice-system-for-organizing-and-tagging-github-issues),
+  by the folks at Robin
+
+
+## License
+
+This work is licensed under a Creative Commons Attribution 3.0
+Unported License.
+<http://creativecommons.org/licenses/by/3.0/legalcode>