* Add more exempt tags for stalebot; Make stalebot to close PRs/issues in 21 days rather than in 7/14 days
* Exempt labels only for issues, not PRs; Add 'Uncategorized problem report' tag
* Add the pull-request template
* Rewording
* Replaced checklist link, added Rat exclusion
* Update the PR template. Add Concurrency Checklist to the repository
* Merge Description and Design sections. Softer language. Removed requirement to test in production environment. Added a committer's instruction to justify addition of meta tags.
* Rephrase item about comments
* Add license header
* Add item to concurrency checklist
* Stalebot config adjustments.
- Different wordings for PRs and issues.
- Extend stale timeout for issues.
- Exempt "Proposal" label.
- Exempt issues in projects and issues with assignees.
* Fix copy/paste error.