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# Objective This PR begins integrating the new releate-content drafting process (https://github.com/bevyengine/bevy/pull/18427) into our GitHub workflows. It's similar to what we had before: Messages are posted to PRs tagged with `M-Needs-Release-Note` or `M-Needs-Migration-Guide` asking them to add the required material and linking to the instructions. These messages do not trigger if the PR already has modified files in the `release-notes` or `migration-guides` directories (respectively). I have also re-arranged and content slightly (to remove the need for a directory with the current version number), tweaked the language, and switched the templates to use the [standard markdown frontmatter format](https://jekyllrb.com/docs/front-matter/). ## Reviewer Questions + Do we want to add a CI rule actually requiring tagged PRs to create/modify files in the correct directories, or is the message prompt enough? + Do we want to add a CI rule to lint the metadata, for example to enforce that the PR number is included in the files it modifies?
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Bevy's Migration Guide Process
Hi! Did someone add M-Needs-Migration-Guide to your PR? If so, you're in the right place.
Let's talk about how this process works.
When we make breaking changes to Bevy, we need to communicate them to users so their libraries and applications can be moved to the new Bevy version. To do this, we write and ship a migration guide for every major Bevy version. To avoid a crunch at the end of the cycle as we write all of these, Bevy asks authors (and reviewers) to write a draft migration guide as part of the pull requests that make breaking changes.
Where to put your migration guides
Each major Bevy version (e.g. 0.12, or 2.0) will get its own migration guide.
The draft migration guides for the current cycle are organized in the bevyengine/bevy/release-content/migration-guides folder.
When we publish our first release candidate for a cycle, these notes are merged together and moved from bevyengine/bevy into bevyengine/bevy-website,
where they will receive a final editing pass.
If your PR introduces a new breaking change relative to the previous version, you should start a new guide by copying the template into a new file in the migration-guides folder.
You should also update the existing migration guides in the other files, if your change effects them.
What to put in your draft migration guide
Migration guides are intended to briefly communicate:
- what has been changed since the last release?
- why did we make this breaking change?
- how can users migrate their existing code?
Draft migration guides do not need to be polished: it's okay if you're not a native English speaker or aren't a wordsmith. Editing is easy; we just want to have an expert's view on the questions above.
When writing migration guides, prefer terse, technical language, and be sure to include terms that users might search for. Migration guides are not read end-to-end: instead, they are navigated via Ctrl+F as the reader follows the compiler errors and bugs.
Grouping changes into migration guides
Migration guides should reflect the complete experience of migrating from the last major Bevy version to the next one. If there are multiple breaking changes layered on top of each other, you should edit the existing migration guide, rather than write a new one.
While some brave users live on Bevy's main branch, we can trust them to use the draft migration guides and read the PRs in question if needed.
As a result, each draft migration should be given a clear name matching the section title. These titles should reflect the name of the old feature that was broken or changed.
Note on the #[deprecated] attribute
Rust provides a very helpful #[deprecated] attribute, which is a compiler-aware way to mark a piece of Rust code as obsolete and slated for removal.
This can be a nice a tool to ease migrations, because it downgrades errors to warnings and makes the migration information available right in the user's IDE.
However, it's not always possible to use this attribute, and Bevy does not consider it to be a substitute to a migration guide entry.